Duramax 6600 updates & new features booklet (english)

Duramax 6600
Updates and New
Features
Course #16340.50B

Caution
In order to reduce the chance of personal injury and/or property damage,
carefully observe the following information:
The service manuals of General Motors Corporation are intended for use by
professional, qualified technicians. Attempting service procedures without the
appropriate training, tools, and equipment could cause personal injury, vehicle
damage, or improper vehicle operation. Proper vehicle service is important to
the safety of the service technician and to the safe, reliable operation of all
motor vehicles. If a replacement part is needed, use the same part number or
an equivalent part. Do not use a replacement part of lesser quality.
The service manuals contain effective methods for performing service
procedures. Some of the procedures require the use of tools that are designed
for specific purposes.
Accordingly, any person who intends to use a replacement part, a service
procedure, or a tool that is not recommended by General Motors, must first
establish that there is no jeopardy to personal safety or the safe operation of
the vehicle.
The service manuals contain Cautions and Notices that must be observed
carefully in order to reduce the risk of injury. Improper service may cause
vehicle damage or render the vehicle unsafe. The Cautions and Notices are
not all-inclusive. General Motors cannot possibly warn of all the potentially
hazardous consequences that may result by not following the proper service
procedures.
The service manuals cover service procedures for vehicles that are equipped
with Supplemental Inflatable Restraints (SIR). Failure to observe all SIR
Cautions and Notices could cause air bag deployment, personal injury, or
otherwise unneeded SIR repairs. Refer to the SIR component and wiring
location views in Restraints before performing a service on or around SIR
components or wiring.
If multiple vehicle systems are in need of repair, including SIR, repair the SIR
system first to reduce the risk of accidental air bag deployment and personal
injury.

Duramax 6600 Updates and New Features
i
Foreword
This manual contains diagnostic and service information regarding the Duramax 6600 Diesel Engine (LLY); including
features that make it unique, basic operation and service strategies, including tools required for service. Always refer
to the applicable vehicle Service Information and appropriate Dealer Technical Service Bulletins for additional
information regarding specific system operation and diagnostic/repair procedures.
When this manual refers to a brand name, a number, or a specific tool, you may use an equivalent product in place
of the recommended item, unless instructed otherwise.
All information, illustrations, and specifications in this manual are based on the latest product information available
at the time of publication approval. General Motors reserves the right to make changes at any time without notice.
When technical assistance is required, call the Technical Assistance Center at 1-877-446-8227.
Published by General Motors Corporation, Service Operations, Warren, Michigan 48090-9008.
© 2005 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.
LITHO IN U.S.A.
No part of this book may be reproduced, stored in any retrieval system, or transmitted in any form or by any means
(including but not limited to electronic, mechanical, photocopying, and recording) without prior written permission of
General Motors Corporation. This applies to all text, illustrations, tables and charts.
All product names throughout this book are trademarks or registered trademarks of their respective holders.

Table of Contents
ii
1. Introduction ......................................................1-1
Introduction ......................................................1-1
2. Engine Mechanical Updates...........................2-1
InternalEngineUpdates ...................................2-1
Block ................................................................2-1
Pistons .............................................................2-1
Cylinder Heads and Gaskets ............................2-1
Connecting Rod Bushings and
Journal Bearings ............................................2-1
Scissor Type Cam Gear ...................................2-2
ExternalEngineUpdates ..................................2-4
TurboVanes.....................................................2-4
EGRCooler ......................................................2-4
Air Induction System ........................................2-5
Intake Air Heater ..............................................2-6
Intake Air Temperature Sensor 2 (IAT 2) ..........2-7
Cooling System ................................................2-8
Exhaust System ............................................2-11
3. 2006 Express and Savana Full-size Van........3-1
2006 Chevrolet Express and GMC
Savana Update ..............................................3-1
Full-Size Van Introduction ................................3-1
Express and Savana Electric Fuel
Prime Pump ...................................................3-2
Transmission....................................................3-2
Prime Pump Service Tools...............................3-3
Fuel Injector Access ........................................3-4
Express and Savana Fuel Operated
Coolant Heater ...............................................3-5
CoolantHeaterOperation .................................3-6
Coolant Heater Scan Tool Access ...................3-6
4. Fuel System Updates ......................................4-1
Revised Fuel Injection System ..................4-1
Injection Flow Rate Programming ..............4-2
Fuel Injector Flow Rate
ProgrammingServiceScenarios................4-3
Injector Flow Rate Programming
Procedures ..............................................4-4
Fuel System Electrical Changes................4-6
5. Electrical System and Engine
ControlsUpdate ...............................................5-1
E35 Engine Control Module (ECM) ...................5-1
Glow Plug Control Module ................................5-4
Special Tools ...................................................5-4
Manifold Absolute Pressure (MAP)
Sensor and BARO Sensor..............................5-6
Intake Air Temperature (IAT 2) Sensor .............5-7
Exhaust Gas Recirculation (EGR) System .......5-7
Intake Air Heater ..............................................5-8
Appendix: 2006 Duramax LLY Engine Controls and
DTC Overview ....................................................... A1
Contents .......................................................... A-1
A. Misfire Monitoring System ......................... A-1
B. Fuel Monitoring System............................. A-1
C. Thermostat Monitoring System
(P0128) ................................................... A-2
D. Exhaust Gas Recirculation (EGR)
System Monitoring ................................. A-2
E. Engine Controls Component DTC List ...... A-3
1. Fuel Injector Control Circuits .............. A-3
2. Crankshaft Angle Sensor .................... A-3
3. Camshaft Angle Sensor...................... A-4
4. Manifold Absolute Pressure Sensor ... A-4
5. Barometric Pressure Sensor .............. A-5
6. Intake Air Temperature Sensor........... A-5
7. IntakeAirTemperature
Sensor 2 (IAT2) ................................ A-6
8. FuelTemperatureSensor ................... A-6
9. EngineCoolantTemperatureSensor .. A-7
10. Mass Air Flow Sensor ........................ A-7
11. TurbochargerBoostControl
Position Sensor ............................... A-8
12. TurbochargerBoostControlSolenoid
Circuit ............................................. A-8
13. Glow Plug Control Module
and Glow Plugs ............................... A-8
14. Memory(ROM/RAM) .......................... A-9
15. Malfunction Indicator (MIL) Lamp ....... A-9
16. Wait To Start (WTS) Lamp ................. A-9
17. ECM - TCM Communications ............. A-9
18. Vehicle Speed Sensor ...................... A-10

1. Introduction
1-1
Figure 1-2, The 2006 Duramax 6600
(full-size van application)
Figure 1-1, The Duramax 6600 for 2006
(Express/Savana version)
Introduction
This course describes the technological
enhancements that the Duramax 6600 engine received
for the 2006 model year.
The 6.6 liter diesel Duramax engine has been
continuously refined each year since its introduction in
2001. It received extensive modifications with the
introduction of RPO LLY VIN Code 2. The benefits
included increased torque output and lower exhaust
emissions.
The latest updates, covered in this course, are aimed
at further refining the engine's operation while
continuing to enhance durability.
The Duramax engine also becomes more widely
available in 2006 when it is offered as an optional
powerplant for Chevy Express and GMC Savana Full-
Size Vans (Fig. 1-2). The engine will remain as an
option for all current applications.

2. Engine Mechanical Updates
2-1
Figure 2-1, 2006 Duramax 6600 Engine
Block
Figure 2-2, New Cylinder Heads and
Gaskets
Internal Engine Updates
Block
Cylinder block casting and machining processes are
changed to provide the cast iron block (Fig. 2-1) with
more bulkhead reinforcement for increased reliability
anddurability.
Pistons
The pistons are revised with a new design that helps
lower the engine's compression ratio from 17.7 to 1 to
16.8 to 1.
Cylinder Heads and Gaskets
New cylinder heads and head gaskets (Fig. 2-2) are
used to accommodate the lowered compression and
increased firing pressure. The lowered compression
ratio serves to reduce engine noise at idle and improve
overall smoothness.
Connecting Rod Bushings and Journal
Bearings
The connecting rod bushings and journal bearings are
also revised for increased durability.

2-2
Figure 2-3, New Cam (Scissor) Gear
Figure 2-4, Inside the Cam Gear is a
C-type Torsion Spring
Scissor Type Cam Gear
One of the most significant mechanical modifications to
the 2006 Duramax is a new camshaft gear (Fig. 2-3).
The gear is a spring-loaded design, usually referred to
as a "scissor" gear. It consists of two gear halves
sandwiched over a C-type torsion spring (Fig. 2-4).

2-3
Figure 2-5, "Scissored" Cam Gear Teeth
Figure 2-6, Meshed Cam Gear Teeth
When the gear teeth are in mesh with another gear, the
spring forces the two gear halves to move
(Fig. 2-5), relative to one another, until the tooth space
on the mating gear is filled. This scissor action of the
gear halves is what gives the gear its name.
The chief advantage of this type of gear is that the
spring action keeps the drive gear and driven gears in
constant mesh (Fig. 2-6). This eliminates backlash and
helps reduce gear noise. Also, the spring loading
automatically adjusts gear contact to compensate for
wear or thermal dimensional changes.

2-4
Figure 2-7, A Lock Bolt through Gear
Halves Neutralizes Spring
Tension
Figure 2-8, EGR Cooler
Before removing the cam gear for service, you must
insert a lock bolt through the gear halves to neutralize
the spring tension (Fig. 2-7). With the lock bolt
installed, you can safely remove the bolt retaining the
cam gear to the shaft.
Never loosen the cam gear retaining bolt without
first inserting the lock bolt.
External Engine Updates
Turbo Vanes
The vanes in the variable-geometry impeller system
are modified so that the turbocharger is more
aerodynamically efficient. This change enhances the
turbocharger's ability to deliver smooth and immediate
response while further reducing emissions.
EGR Cooler
The EGR cooler (Fig. 2-8) that was introduced on the
2004 LLY engine is enlarged to provide increased
exhaust gas cooling capacity.

2-5
Figure 2-9, Air Intake Components for
Duramax-Equipped Express
Full-Size Vans
Figure 2-10, Revised Air Intake
Components for Duramax-
Equipped Light-Duty Trucks
Air Induction System
There are a number of modifications in the engine
cooling and air induction systems for 2006 models. A
new fan is used and the fan clutch is also a new
design. The engine-mounted fan shroud and mounting
brackets are also new.
The entire air induction system is retuned for more
efficient, quieter operation.
New induction components include the air filter, air
box and the duct between the filter box and the
turbocharger inlet (Figs. 2-9, 2-10).

2-6
Figure 2-12, IAH for Light-Duty Truck
(Left) and Full-Size Van
(Right) Applications
Figure 2-11, Intake Air Heater (IAH)
Intake Air Heater
A new intake air heater (IAH) is also used on the 2006
LLY (Fig. 2-11). Heating the intake air helps to reduce
smoke and emissions during cold or light-load driving.
The IAH features a grid heater (Fig. 2-12), which is
triggered automatically by the ECM to reduce white
smoke during cold weather operation.

2-7
Figure 2-14, Additional Intake Air
Temperature (IAT 2) Sensor
Figure 2-13, IAH Mega Fuse
Intake Air Temperature Sensor 2 (IAT 2)
There is an additional intake air temperature sensor
(Fig. 2-14), located on the right side of the intake
manifold. The second sensor provides the ECM with
temperature of the actual combustion air as it enters
the cylinders.
The ECM uses this data in its timing and fuel
adjustment calculations to help reduce emissions. A
secondary function for the second IAT 2 sensor is
control of the EV fan.
Power for the IAH is provided through an added 175
amp mega fuse (Fig. 2-13).

2-8
Figure 2-16, Radiator & Fan Shroud
Figure 2-15, Water Pump
Cooling System
A larger volume water pump (Fig. 2-15) is used on the
2006Duramax.
A larger radiator is used and the upper and lower
radiator shrouds and support are redesigned.
Mounting the fan shroud directly to the engine
provides increased cooling ability.

2-9
Figure 2-18, Larger, Quick-Connecting
Lower Radiator Hose
Figure 2-17, Radiator Baffle
A new radiator baffle (Fig. 2-17) is common to both
Chevrolet and GMC applications.
The lower radiator hose is also larger for increased
coolant flow (Fig. 2-18). A new quick-connect
attachment connects the hose to the radiator.

2-10
Figure 2-20, Auxiliary Transmission
Cooler and Lines
Figure 2-19, Charge Air Cooler Duct with
Quick-Connects
An updated auxiliary transmission fluid cooler
(Fig. 2-20) has been added. The oil cooler lines are
also new.
Quick connects are also used on the new cold-side
Charge Air Cooler duct (Fig. 2-19).
Because of the change in the duct between the charge
air cooler and intake air heater, a new tool, J46091-5,
Charge Air Cooler Tester Adapter (not shown) is
required for light-duty truck applications.

2-11
Figure 2-21, "Torca" Exhaust Clamp
Exhaust System
On light-duty truck applications, a "Torca" style band
clamp (Fig. 2-21) is now used between the exhaust
downpipe and the rear muffler.

Notes
2-12

3. 2006 Chevrolet Express and GMC Savana Update
3-1
Figure 3-1, Duramax 6600 Full-Size Van
Application
Figure 3-2, Revised Instrument Panel
2006 Chevrolet Express and
GMC Savana Update
Full-Size Van Introduction
For the 2006 model year, the 6.6L Duramax 6600
turbodiesel V-8 will be available in the Chevrolet
Express and GMC Savana full-size G-vans (Fig. 3-1).
To support the new powertrain, Express and Savana
models equipped with the Duramax 6600 also include:
• Revised front floor panel and
underbodyheatshielding
• New interior engine cover
• High idle switch added to instrument
panel(optional)
• Instrument cluster revised to reflect
diesel engine functionality (Fig. 3-2)
• Standard145-ampalternator
• Primary battery located underhood,
with secondary battery mounted on
left-hand frame rail
• Ambulance package equipped with a
50-amp Maxi fuse connector at the
B-pillar

3-2
Figure 3-3, Hydra-Matic 4L85-E
Figure 3-4, Full-Size Van Fuel Prime
Pump (Left)
Transmission
When the Duramax is used in full-size van
applications, it is teamed with the Hydra-Matic 4L85-E
heavy-duty transmission (Fig. 3-3).
Express and Savana Electric Fuel Prime
Pump
Some additional components are used for the Duramax
engines used in the full-size Chevy Express and GMC
Savana van.
An electric fuel prime pump (Fig. 3-4), mounted on the
frame rail of the van, replaces the hand pump in all
Duramax-equipped full-size vans. A fuel filter is located
beside the pump.
There is also a removable filter located on the prime
pump. The recommended service interval in the
Duramax owner's guide Maintenance II schedule should
be followed as a guide for replacing both of these
filters.

3-3
– IMPORTANT –
The fuel prime pump must be disabled before using the existing vacuum gauge to
diagnose the fuel system. The pressure with the pump running can reach 276 kPa
(40 psi), much more than the 69 kPa (10 psi) the gauge is designed to handle.
Figure 3-5, EN47620 - Fuel Pressure
Gauge Adapter
Figure 3-6, EN47969 - Fuel Supply
Diagnostic Hose
Prime Pump Service Tools
There are two special service tools associated with the
prime pump. These are a Fuel Pressure Gauge
Adapter, tool number EN47620 (Fig. 3-5) for use with
the existing fuel pressure gauge J 34730-1A to
diagnose prime pump concerns.
The fuel pressure kit is J 34370
There is also a clear fuel supply diagnostic hose
EN47969 (Fig. 3-6) that can also be used for fuel
system diagnosis on all LLY applications.

3-4
Figure 3-7, Access Panel for #5 Fuel
Injector (Seen From the
Passenger Compartment)
Figure 3-8, Access Panel Removed
Fuel Injector Access
Because of the positioning of the Duramax engine in
the full-size Chevrolet and GMC Vans, a removable
body panel (Fig. 3-7) is provided to allow access to the
number 5 fuel injector (Fig. 3-8).

3-5
Figure 3-9, Fuel-Operated Coolant
Heater
Figure 3-10, Coolant Heater Exhaust
The fully integrated Fuel Operated Heater system is
designed into the Express and Savana chassis, saving
owners the time and labor of upfitting an aftermarket
system; an industry-first for full-size vans. Similar
style heaters are often used on recreational and other
commercial vehicles.
The unit features a self-contained, pressurized coolant
heater, that uses diesel fuel to generate up to 17,200
Btu/h (5 kw) of heating energy.
The coolant heater is equipped with an exhaust system
(Fig.3-10).
Express and Savana Fuel Operated Coolant
Heater
A unique option available for Duramax-equipped 2006
Full-Size Vans is a factory-installed, fuel-operated
heater (Fig. 3-9) that provides auxiliary engine coolant
heating in cold weather. In Service Information, the
unit is referred to as the coolant heater, RPO code
K08.

3-6
The electronically controlled, coolant heater operates automatically, turning on and off within set parameters. The
heater only runs when the engine is already running and its operation is fully integrated with the vehicle's coolant
and fuel systems.
Coolant Heater Operation
The Coolant Heater turns ON when:
• Outside air temperature <= 39° F (4° C)
• Engine is running
• Fuel level > 12.5% total volume of fuel tank
• Coolant temp <= 167° F (75° C)
The Coolant Heater turns OFF when:
• Outside air temperature > 39° F (4° C)
• Engine is not running
• Fuel level < 12.5% total volume of fuel tank
• Coolant temp >= 185° F (85° C)
Coolant Heater Scan Tool Access
Operation of the heater can also be monitored with the scan tool.
The scan tool navigation path for accessing coolant heater data is as follows:
– Diagnostics
– 2006
– LD Trk, MPV, Incomplete
– Chevrolet Truck/GMC Truck
– G
– Express/Savana
– Powertrain
– 6.6 L V8 LLY Diesel
F0: Diagnostic Trouble Codes (DTC)
F1: Data Display
F2: Auxiliary Heater Data Display
F2: Special Functions
F3: Auxiliary Heater Output Controls
F3: Snapshot
F4: I/M System Information
F5: Calibration ID
– AuxiliaryHeaterModule
– SoftwarePartNumber
– ModelNumber

4. Fuel System Update
4-1
Figure 4-1, Fuel Pump
Figure 4-2, Redesigned Fuel Injector
Revised Fuel Injection System
One of the major enhancements for the latest
Duramax 6600 is the revised fuel injection system. A
new fuel pump design (Fig. 4-1) increases fuel
pressure in the common-rail system from 23,200 psi
(160 MPa) to 26,000 psi (180 MPa).
An important point to note on the 2006 engine is that,
if the monitored fuel pressure rises above the
maximum, the pressure relief valve opens and
remains open until the engine is shut OFF. When the
valve opens, the pressure drop in the rail will cause
DTC P0087: Fuel Rail Pressure (FRP) too low to set.
The fuel injectors (Fig. 4-2) themselves are also new
and feature a 7-hole spray nozzle that helps to more
finely atomize the fuel spray in the cylinder. The
injectors are positioned in the head so that they spray
directly on the glow plugs to aid fast start-up in cold
conditions (Fig. 4-3).
Figure 4-3, Injector Spray Pattern

4-2
Figure 4-5, Injection Flow Rate Value
Being Read
Figure 4-4, Fuel Injector Imprinted with
Injection Flow Rate
Programming Value
Injection Flow Rate Programming
During the fuel injector manufacturing process, each
injector is tested and its flow rate is measured at
several points. These measurements are recorded as
the Injection Flow Rate value. This data is then
recorded on a bar code label and laser etched as a hex
number on the body of the injector (Fig. 4-4) before it
is shipped to the Duramax engine assembly plant.
As the injectors are installed on the engine in the
Duramax manufacturing plant, the bar code is read
(Fig. 4-5) on each injector and then stored in the
DMAX computer system, along with the cylinder
location in which the injector is installed.
This information is also transmitted to a factory Fuel
Bleed Machine that writes the information to the Glow
PlugControlModule.
– NOTE –
Due to changes made after the completion of the video, some of the terminology used in the following Injection
Flow Rate Programming sections varies from the video. This booklet contains the most current terminology.

4-3
Figure 4-6, Injection Flow Rate Values
Stored in the ECM and GPCM
During final vehicle assembly, the value and cylinder
position information from the GPCM is copied and
written to the ECM memory when it is installed in the
truck and the EE PROM is flashed. The vehicle leaves
the assembly plant with two identical copies of stored
values, one in the GPCM and one in the ECM
(Fig. 4-6).
During engine operation, the ECM uses Injection
Quantity Adjustment (IQA) calibrations, based on the
injection flow rate values, to more precisely adjust the
fuel injection quantity for each cylinder. This
contributes to combustion efficiency and reduced
emissions.
When the ignition is turned on, both the glow plug
control module and the ECM check that injection flow
rate values for all injectors are flashed in memory. If
any value is missing, the Glow Plug Control Module
sets code P160C signifying that injection flow rate
values are not programmed in its memory. Similarly the
ECM will set code P268A to signal that the injection
flow rate values are not programmed.
Fuel Injector Flow Rate
Programming Service Scenarios
There are a number of fuel system service situations
where injector and module programming will directly
affect service procedures and related service
information.
Situations include:
• Injectorreplacement
• ECM service or replacement
• Glow Plug Control Module service or
replacement.
Performing any of these procedures could result in a
condition where the injection flow rate values stored in
the modules does not match the injector. Injectors
beingswappedduringdiagnosis(NOTrecommended)
could also produce the same result.
For example, while diagnosing an engine performance
concern, a technician swaps injectors between
cylinders. He observes no difference in engine
performance and continues with the repair. After
completing repairs, he forgets to return the injectors to
their original cylinder positions.
The engine may run properly but the values in the
ECM and GPCM will be different. This could lead to
confusion the next time the vehicle is serviced, or if
another symptom occurs.
The important point to remember is that the
relationship of the injector flow values in the ECM, the
Glow plug control module and the injectors must be
maintained in order for the fuel delivery system to
function as it is designed. Do not swap parts from
other vehicles when performing fuel system diagnosis
and repairs. Use only service replacement parts for
your repairs and the service programming procedures
will ensure that the correct injection flow rate value
relationships are maintained for the vehicle.

4-4
Figure 4-8, Injector Flow Rate
Programming Data Display
Figure 4-7, Injector Flow Rate
Programming Menu
Figure 4-9, Reprogramming Injector Flow
Rate Values for a New Injector
Selecting F0: Display ECM and GPCM Inj. Flow
Rates, allows for the viewing of the current injector
flow rate values stored in both the ECM and GPCM for
each injector (Fig. 4-8).
Selecting F1: Reprogram Injector Flow Rates, allows
for the reprogramming of individual injector flow rate
values into both the ECM and GPCM after an injector
is replaced (Fig. 4-9).
Injector Flow Rate Programming
Procedures
The tech 2 is used to program individual injectors, the
ECM and the GPCM. The Tech 2 programming path is
as follows:
– Build the vehicle
– Select"Powertrain"
F2: Special Functions
F2: Fuel System
F4: Injector Flow Rate Programming
This will lead to the Injector Flow Rate Programming
menu (Fig. 4-7).

4-5
Figure 4-10, Copy GPCM Injector Flow
Rate Values to ECM
Figure 4-11, Copy ECM Injector Flow Rate
Values to GPCM
Selecting F3: Copy ECM Inj. Flow Rates to GPCM,
allows for the copying of the flow rate values for all
eight injectors from the ECM to the GPCM when a new
GPCM is installed (Fig. 4-11).
Selecting F2: Copy GPCM Inj. Flow Rates to ECM,
allows for the copying of the flow rate values for all
eight injectors from the GPCM to the ECM when a new
ECM is installed (Fig. 4-10).

4-6
Fuel System Electrical Changes
As on the previous Duramax 6600, the ECM controls
the common fuel rail pressure using the fuel rail
pressure regulator on the fuel injection pump and
monitors voltage feedback from the fuel rail pressure
sensor. For 2006, the pressure sensor is relocated to
end of the right side fuel rail (Fig. 4-12).
An added DTC, P0191, now sets when the ECM
detects that FRP sensor voltage is out of range
compared to the atmospheric pressure.
Fuel Injection diagnostic circuits have also been
modified.
As before, there are high and low side fuel injector
control circuits.
The DTC numbers P0201 through P0208 for the eight
injector control circuits remain unchanged.
On the 2005 Duramax LLY, voltage control circuits are
divided into two groups of 4 cylinders each. On the new
LLY there are four groups of cylinder voltage circuits.
So there are 2 cylinders on each group (Fig. 4-13).
Injector driver chips have internal diagnostics that
detect electrical faults, such as opens, shorts to
voltage and shorts to ground. When an error is
detected, a 32 bit message enables the ECM to
determine the injector number, injector driver group
number and the injector driver chip number.
If only the individual injector code, P0201 through 8
sets, only the affected injector is shut off.
If a DTC is set for the injector driver group, both
injectors in the affected group are turned OFF.
Figure 4-12, Fuel Rail Pressure Sensor

4-7
Figure 4-13, 2006 Duramax Fuel Injection Circuits

Notes
4-8

5. Electrical System and Engine Controls Update
5-1
Figure 5-1, Bosch E35 ECM
E35 Engine Control Module (ECM)
The control functions for the fuel injection system are
now integrated in the vehicle's Engine Control Module
or ECM. The 2006 Bosch-manufactured ECM (Fig. 5-1)
incorporates the first application of a more powerful
E35 controller. This 32-bit processor can support up to
five injection pulses per combustion event.
Because of the added processing power this Bosch
E35 controller provides, the separate Fuel Injection
Control Module or "FICM" that was used in previous
model years is not required. The injector circuit cooling
function that was previously a function of the FICM is
also not needed because the new injector system
operating voltage is less than half that of the previous
system and circuit heating is not an issue.
During the manufacturing processes, the flow quantity
of each injector is measured and this data, together
with the injector's cylinder position, is stored in the
memory of both the Glow Plug Control Module and the
ECM.
The 32-bit ECM can use injector flow data to precisely
meter fuel delivery to individual cylinders and
compensate for flow variations among individual
injectors.
Some of you may be familiar with the similar QR
injector ID codes that are used on the Duramax 7.8
liter, LG4 engine. When an injector is newly installed in
a vehicle, it is necessary to update the ID codes in the
ECM.

5-2
Figure 5-2, ECM Wiring Harness

5-3
Figure 5-3, TCM and ECM
Figure 5-4, Glow Plug Control Module
With the new Bosch ECM and the Transmission
Control Module, the wiring harness connection is
modified.
The ECM now uses two cam-lock connectors instead
of three.
The wiring harness itself is modified to provide a direct
connection between the ECM and battery positive
(Fig. 5-2).
Engine Control Module DTC Update
The 2006 Duramax LLY ECM, TCM and GPCM
(Figs. 5-3, 5-4) communicate over the GM Local Area
Network or GMLAN. All other modules continue
communicate with the ECM via class 2.
If the ECM does not receive messages from the Glow
Plug Control Module on the GMLAN, DTC U0106 is
set.
There are a number of new DTC's for the ECM itself.
The following codes set when the ECM detects errors
in its internal processors and functions:
P060B - Control Module Analog to Digital Performance
P061C - Control Module Engine Speed Performance
P062C - Control Module Vehicle Speed Performance
P062F - Control Module Long Term memory
Performance
Revised Glow Plug Control Module and GPCM DTC
Update

5-4
Figure 5-6, Leak-Down Tester Adapter
J35667-8 and Compression
Gauge Adapter EN47603
Figure 5-5, Glow Plug Control Module
(Full-Size Van Application)
Special Tools
Incidentally, because the new glow plugs have different
thread locations than the previous models, new
adapters are required for cylinder test tools that use the
glowplugopening.
The new cylinder head leak-down tester adapter is
J35667-8 and the new compression gauge adapter is
EN47603 (Fig. 5-6). The actual test procedures are
unchanged.
Glow Plug Control Module
The Glow Plug Control Module (Fig. 5-5) is a new
design, as are the glow plugs themselves.
The Glow Plug Control Module uses the same DTCs
for the individual glow plugs as the previous model.
DTC's P0671 through 0678 identify the status of each
glow plug circuit (Fig. 5-7).
A new code P064C, Glow Plug Control Module
Performance sets if an error is detected within the
controlmodule.

5-5
Figure 5-7, Glow Plug Control Circuit

5-6
Figure 5-8, Manifold Absolute Pressure
(MAP) Sensor
Manifold Absolute Pressure (MAP)
Sensor and BARO Sensor
New for 2006 is the addition of a Manifold Absolute
Pressure, or MAP, sensor (Fig. 5-8). The MAP sensor
responds to pressure changes in the intake manifold
that vary with engine speed and load.
The MAP sensor performs the functions that were
performed by the turbo boost sensor on the 2005
Duramax. The sensor was renamed to conform to
Federally-mandatedindustrystandards.
Also on the 2006 Duramax, the BARO sensor is
incorporated into the ECM. The ECM uses the BARO
voltage signal to calibrate the fuel injection quantity
and injection timing for altitude compensation.
The ECM can detect a biased sensor by comparing the
BARO and MAP signals at key ON and idle when both
sensors are exposed to atmospheric pressure and
should be the same.
DTC P0106 is set if the ECM detects that the signals
from the MAP sensor BARO sensor do not correlate.
Additional DTCs are included for when the ECM
detects MAP Sensor Circuit voltage is lower or higher
than the calibrated voltage.
Manifold Absolute Pressure (MAP) Sensor Circuit Low/
High Voltage - P0107/P0108.
The ECM uses MAP sensor data to determine when
turbo charger over or under boost conditions are
present. The DTCs remain the same as before
although the calculations have changed.
The ECM checks the turbocharger vane position
sensor readings while the vanes are being
commanded. DTC P2563 sets if the actual vane
position varies from the commanded position by more
than 15 percent.
A new DTC, P003A, replaces P0046 and sets if the
position sensor shows that signals from the vanes are
outside a calibrated specification.

5-7
Figure 5-10, Intake Air Temperature
(IAT 2) Sensor
Figure 5-9, EGR System
Intake Air Temperature (IAT 2) Sensor
A second Intake Air Temperature sensor (Fig. 5-10),
located in the center intake manifold, is used in
conjunction with the added intake air heater.
The second sensor is identified as IAT 2 and functions
identically to Sensor 1. DTCs for the IAT Sensor 2 Low
and High voltage are P0097 and P0098 respectively.
Exhaust Gas Recirculation (EGR) System
There are also some new DTCs for the EGR system.
P0402 now sets when the ECM detects that EGR flow
is excessive. This compliments the existing code
P0401 for insufficient flow.
There is also an updated code, P046C, EGR Position
Sensor Performance, for when the desired EGR valve
position does not match the actual position, indicating
the valve may be stuck.

5-8
Figure 5-11, Intake Air Heater (Full-Size
Van Application)
Intake Air Heater
The GPCM uses the Intake Air Heater (Fig. 5-11)
feedback to monitor multiple circuits for a number of
conditions.
P0540 Sets If:
• No current detected through heater
grid.
• Low current detected through heater
grid.
• IAH Overtemp.
• IAH Over or under voltage.
• Groundopen.
• IAH Switch defective.
• Temperature line open or shorted.
• IAH Resistance too high.
Refer to the most current Service Information for
specific details and service procedures for the new fuel
system and engine controls data.

Appendix
Appendix-1
2006 Duramax LLY Engine Controls and DTC Overview
Contents
A) MisfireMonitoring
B) Fuel System Monitoring
C) ThermostatMonitoring
D) Exhaust Gas Recirculation (EGR) System Monitoring
E) ComprehensiveComponentList
A. Misfire Monitoring System
Misfire monitoring is a function of the variation in crankshaft rotating speed, which is a function of the variation in
torque resulting in a misfire. The minimum average cylinder speed is sensed on the basis of signals from the
crankshaft angle sensor. This minimum speed is calculated every 2 engine revolutions. In addition, the camshaft
angle sensor signals are also used to monitor cylinders position to determine in which cylinder the misfire occurred.
As soon as the actual cylinder speed falls below the minimum average cylinder speed, a misfire is sensed and a
misfire counter is updated.
Misfire monitoring operates as on previous versions of the Duramax. Injector balance rates are a factor in
determining misfires. For more information on misfire monitoring, see DTC codes P0300 - P0308 in Service
Information.
B. Fuel Monitoring System
A target rail pressure is determined to obtain desired performance and emissions. The target fuel pressure in the
common rail is maintained by modulating the duty cycle of the rail pressure control valve. The fuel pressure control
valve is controlled by a Low Side Driver on the ECM. The fuel rail pressure sensor provides the feedback used in
this control.
The following monitors diagnose this system:
Fuel Rail Pressure [FRP] Too Low - P0087
Detects a rail pressure below a minimum threshold OR a rail pressure delta below the target pressure.
Fuel Rail Pressure [FRP] Too High - P0088
Detects a rail pressure above a maximum threshold OR a rail pressure delta above the target pressure.
Fuel Pressure Regulator Control Circuit - P0090
Detects opens and shorts checks on the Fuel Pressure Regulator Control Circuit using the ECM electronic output
driver circuitry fault detection.
Fuel Rail Pressure [FRP] Sensor Performance - P0191
Detects in range sensor faults by comparing the sensor voltage when the common rail is not being pressurized to a
voltage range corresponding to atmospheric pressures.
Fuel Rail Pressure [FRP] Sensor Circuit Low Voltage - P0192
Detects circuit shorts to ground causing a low voltage condition on the sensor input.
Fuel Rail Pressure [FRP] Sensor Circuit High Voltage - P0193
Detects circuit opens or short to battery causing a high voltage condition on the sensor input.

Appendix
Appendix-2
C. Thermostat Monitoring System (P0128)
Two thermostat valves are used to regulate the coolant flow out of the engine and into the radiator. These
temperature activated valves open when the coolant they are exposed to reaches a certain temperature. 82°C for
one thermostat; 85°C for the second. Restricting the flow of coolant out of the engine maintains a desired engine
operating temperature. The diagnostic detects if the measured coolant temperature fails to reach one of the
following:
• 50°C when the Estimated Ambient Air Temperature < 10°C or
• 72°C when the Estimated Ambient Air Temperature > 10°C.
The performance of the thermostat is checked against a coolant temperature model. The model calculates the rise in
coolant temperature based on factors like fuel consumption and intake air temperature. After the engine starts
running, the model will initialize to the actual coolant temperature. Then as the engine consumes fuel, the model
updates the expected coolant temp. As a result, the diagnostic will fail when one of the following conditions is true:
• Model coolant temperature > 55°C and actual coolant temp < 50°C or
• Model coolant temperature > 80°C and actual coolant temp < 72°C.
This is a model based approach which compensates for elevated start-up coolant and ambient air temps varying
within a the temperature regions.
D. Exhaust Gas Recirculation (EGR) System Monitoring
The EGR system recirculates a portion of exhaust gas into the intake air stream to reduce nitrogen oxides (NOx)
emissions. The EGR valve position is controlled by a DC motor. A position sensor provides feedback on EGR valve
control.
The following monitors diagnose this system:
Exhaust Gas Recirculation Control Circuit - P0403
Detects opens and shorts checks on the EGR control circuit using the ECM electronic output driver circuitry fault
detection.
Exhaust Gas Recirculation Position Sensor Circuit Low Voltage - P0405
Detects low voltage condition on the position sensor circuit due to a short or open circuit.
Exhaust Gas Recirculation Position Sensor Circuit High Voltage - P0406
Detects high voltage condition on the position sensor circuit due to a short-circuit to high voltage.
Exhaust Gas Recirculation (EGR) Flow Insufficient - P0401
Detects decreases in EGR flow sufficient enough to cause emission impacts greater than 1.5 X the standard. The
intake airflow (MAF) is measured during EGR operations and compared to the expected values. As EGR flow is
restricted, MAF values go up beyond what is expected. If failure tolerances are met, the diagnostic code is set.
Exhaust Gas Recirculation (EGR) Flow Excessive - P0402
Detects increases in EGR flow sufficient enough to exceed fault tolerances. The intake airflow (MAF) is measured
during EGR operations and compared to the expected values. As EGR flow increases beyond desired rates, MAF
values go down beyond what is expected. If failure tolerances are met, the diagnostic code is set.
Exhaust Gas Recirculation (EGR) Position Sensor Performance - P046C
Detects increases and decreases in EGR flow caused by a stuck EGR valve. This diagnosis monitors actual EGR
valve position via a position sensor and compares it to desired position. If failure tolerances are met, the diagnostic
code is set.

Appendix
Appendix-3
E. Engine Controls Component DTC List
1. Fuel Injector Control Circuits
a. Fuel Injector Positive Voltage Control Circuits
b. Fuel Injector Output Circuits
2. Crankshaft Angle Sensor
3. Camshaft Angle Sensor
4. Manifold Absolute Pressure (MAP) Sensor
5. Barometric Pressure (BARO) Sensor
6. Intake Air Temperature (IAT) Sensor
7. Intake Air Temperature 2 (IMT) Sensor
8. FuelTemperatureSensor
9. EngineCoolantTemperatureSensor
10. Mass Air Flow (MAF) Sensor
11. TurbochargerVanePositionSensor
12. TurbochargerVaneControlSolenoid
13. Glow Plug Control Module and Glow Plugs
a. Glow Plug Control Module Internal Circuit
b. Glow Plug Circuit
c. GPCM-ECMGMLANCommunication
14. Memory(ROM/RAM)
15. Malfunction Indicator Lamp (MIL) Diagnostic
16. Wait To Start (WTS) Lamp Diagnostic
17. ECM-TCMCommunications
18. Vehicle Speed Sensor (VSS)
1. Fuel Injector Control Circuits
a. Injector X Control Circuit (P0201 - P0208)
The ECM electronic circuit monitors check the injector current during injection events. If errors
are detected the respective injector circuit malfunction code (P0201 - P0208) will set.
b. Injector Positive Voltage Control Circuit Group X (group 1 thru 4)
The ECM electronic circuit monitors, check the four banks of voltage supplies providing power
for the injectors. If errors are detected the respective control circuit group malfunction code
(P2146, P2149, P2152, P2155) will set.
2. Crankshaft Angle Sensor
Crankshaft angle sensor generates fifty-eight (58) pulses per revolution from a special purpose fifty-eight tooth wheel
attached to the engine crankshaft. The pulse is used to locate the cylinder reference event (top dead center) for
each cylinder. The ECM uses the information to optimize timing, trigger real time events and it is intrinsic to the
camshaft angle sensor diagnostic.
Circuit Continuity Check
Crankshaft Position [CKP] Sensor Circuit - P0335
Detects the circuit continuity of crankshaft angle sensor when the ECM recognizes that the engine is rotating based
on the CAM signal.

Appendix
Appendix-4
Rationality Check
Crankshaft Position [CKP] Sensor Performance - P0336
Detects missing or extra crank pulse by signal analysis and correlating CAM and Crank signals.
3. Camshaft Angle Sensor
The CAM position sensor generates 3 pulses per 2 crankshaft revolution. The pulse is used to distinguish whether
the cylinder event is compression top dead center or exhaust top dead center at the beginning of engine start.
Camshaft Position [CMP] Sensor Circuit - P0340
Detects the circuit continuity of camshaft angle sensor when the ECM recognizes that the engine is rotating, based
on the Crank signal.
Rationality Check
Camshaft Position (CMP) Sensor Performance - P0341
Detects missing or extra crank pulse by signal analysis and correlating CAM and Crank signals.
4. Manifold Absolute Pressure Sensor
The manifold absolute pressure sensor measures the intake manifold pressure, which varies depending on engine
speed and load conditions and turbocharger vane position. This pressure is converted to a voltage output, which is
monitored by the ECM in order to optimize fuel and timing. The manifold absolute pressure sensor diagnostic
consists of two parts; a continuity check, and a rationality check.
The continuity check monitors the manifold absolute pressure signal and determines if the signal has spent a
predetermined period of time in an unrealistic region (too high or too low).
Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage - P0107
This check is enabled whenever the PCM is powered up. If the measured sensor output is below a calibration
voltage for a calibration period of time, the test will fail.
Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage - P0108
This check is enabled whenever the PCM is powered up. When the measured sensor output is above a calibration
voltage for a calibration period of time, the test will fail.
Rationality Check
The manifold absolute pressure sensor rationality check verifies the controllability of the manifold pressure under
certain engine speed/load conditions.
Manifold Absolute Pressure (MAP) Sensor Performance - P0106
Detects a bias sensor by comparing MAP and BARO at engine speeds < a calibration. Both of these pressure
sensors exposed to atmospheric pressure should be the same. If they differ by a calibration the code will set. This is
also a rationality for the BARO sensor.

Appendix
Appendix-5
Turbocharger Over Boost - P0234
This diagnostic checks for an over boost condition when:
• The engine is running
• Manifold Absolute Pressure sensor code P2564/P2565 is not set.
The measured boost is compared to the calibrated diagnostic threshold. If the measured boost is outside the
diagnostic parameters a code P0234 is set.
Turbocharger Under Boost - P0299
This diagnostic checks for an over boost condition when:
• The engine is running
• Manifold Absolute Pressure sensor code P2564/P2565 is not set.
The measured boost is compared to the calibrated diagnostic threshold. If the measured boost is outside the
diagnostic parameters a code P0299 is set.
5. Barometric Pressure Sensor
The barometric pressure sensor measures the atmospheric pressure, which varies depending on altitude and weather
conditions. This pressure is converted to a voltage output, which is monitored by the ECM in order to optimize fuel
and timing.
Barometric Pressure (BARO) Circuit Low Input - P2228
Detects a barometric pressure signal that has spent a predetermined period of time in an unrealistic region (too low).
This test runs when the ignition is on.
Barometric Pressure (BARO) Circuit High Input - P2229
Detects a barometric pressure signal that has spent a predetermined period of time in an unrealistic region (too high).
This test runs when the ignition is on.
Rationality Check
The rationality check for the BARO sensor is covered by Manifold Absolute Pressure (MAP) Sensor Performance -
P0106. (see above)
6. Intake Air Temperature Sensor
The intake air temperature sensor is a thermistor type device, located before the turbocharger as part of the MAF
assembly. The resistance of the sensor decreases as the intake air gets hot and increases as the intake air gets
cold. The sensor resistance and a pull-up resistor form a voltage divider in the ECM. The resulting voltage is
measured and converted to a temperature. The control software uses intake air temperature to optimize fuel rate and
timing.
Intake Air Temperature Sensor Circuit Low Voltage - P0112
Detects a low voltage on the temperature circuit. If a predetermined period of time in this unrealistic region passes,
the code will set.
Intake Air Temperature Sensor Circuit High Voltage - P0113
Detects a high voltage on the temperature circuit. If a predetermined period of time in this unrealistic region passes,
the code will set.

Appendix
Appendix-6
7. Intake Air Temperature Sensor 2 (IAT2)
There is an additional intake air temperature sensor located on the right side of the intake manifold. The IAT 2
sensor functions identically to the IAT 1 sensor. It provides the ECM with the temperature of the actual combustion
air as it enters the cylinders.
The ECM uses this data in its timing and fuel adjustment calculations to help reduce emissions.
Intake Air Temperature Sensor 2 Circuit Low Voltage - P0097
the code will set.
Intake Air Temperature Sensor 2 Circuit High Voltage - P0098
the code will set.
Rationality Check
Intake Air Temperature Sensor 1-2 Correlation - P2199
If, at start-up, after a 10 hour engine soak time, the IAT 2 sensor temperature is more than 5.3°C (9°F) higher or
lower than the IAT Sensor, the code will set.
8. Fuel Temperature Sensor
The fuel temperature sensor is immersed in the diesel fuel returning from the fuel system. The resistance of the
sensor decreases as the fuel gets hot and increases as the fuel gets cold. The sensor resistance and a pull-up
resistor form a voltage divider in the ECM. The resulting voltage is measured and converted to a temperature. The
control software uses fuel temperature to compensate for rail pressure.
Circuit Continuity Checks
Fuel Temperature Sensor Circuit Low Voltage - P0182
the code will set.
Fuel Temperature Sensor Circuit High Voltage - P0183
the code will set.
Rationality Check
Fuel Temperature Sensor Performance - P0181
Detects a fuel temperature sensor biased high or low, but still within its normal range.
If the engine has been off, as measured by the ignition off timer, for a sufficiently long period of time, this diagnostic
compares the fuel temperature soon after engine start with the engine coolant temperature soon after engine start. If
the start-up temperature difference between the fuel temperature sensor and the engine coolant temperature (ECT)
sensor is within a calibration amount the diagnostic passes.
If the start-up temperature difference between the fuel temperature sensor and the engine coolant temperature (ECT)
sensor is not within a calibration amount the diagnostic still passes, but block heater influence is tested. Block
heater influence is determined by monitoring the IAT during vehicle drive time at speeds greater than a calibration
and for a calibrated amount of time. If the IAT drops below a calibrated temperature, block heater influence is
suspected and the diagnostic is aborted for this key cycle.
If block heater influence has been ruled out and the sensors being compared do not agree, then the diagnostic will
set for the second key cycle.

Appendix
Appendix-7
9. Engine Coolant Temperature Sensor
The engine coolant temperature sensor is a thermistor type device exposed to the engine coolant. The resistance of
the sensor decreases as the engine coolant gets hot and increases as the engine coolant gets cold. The sensor
resistance and a pull-up resistor form a voltage divider in the ECM. The resulting voltage is measured and converted
to the coolant temperature. The control software uses engine coolant temperature in many algorithms i.e. fueling,
timing and diagnostics.
Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage - P0117
the code will set.
Engine Coolant Temperature (ECT) Sensor Circuit High Voltage - P0118
the code will set.
Rationality Check
Engine Coolant Temperature (ECT) Sensor Performance - P0116
Detects a fuel temperature sensor biased high or low, but still within its normal range.
If at start-up the delta between the engine coolant temperature (ECT) and the intake air temperature (IAT) is less
than a calibrated value, the diagnostic will pass.
If at start-up the delta between the engine coolant temperature (ECT) and the intake air temperature (IAT) is greater
than a calibrated value, block heater influence is tested. Block heater influence is determined by monitoring the IAT
during vehicle drive time at speeds greater than a calibration and for a calibrated amount of time. If the IAT drops
below a calibrated temperature, block heater influence is suspected and the diagnostic is aborted for this key cycle.
If block heater influence has been ruled out, and the sensors compared disagree, the diagnostic will set.
10. Mass Air Flow Sensor
The mass airflow sensor measures the mass of the air flowing in the intake manifold. This flow varies depending on
the engine speed and load conditions. This airflow is converted to a current output, which is monitored by the ECM
in order to optimize fuel and timing. The mass airflow sensor diagnostic consists of two parts, a continuity check
and a rationality check.
Mass Air Flow (MAF) Sensor Circuit Low Voltage - P0102
Detects a signal that has spent a predetermined period of time in an unrealistic region (too low). This check is run
when the engine speed is within a calibration window.
Mass Air Flow (MAF) Sensor Circuit High Voltage - P0103
Detects a signal that has spent a predetermined period of time in an unrealistic region (too high). This check is run
all the time.
Rationality Check
Mass Air Flow (MAF) Sensor Performance - P0101
Detects normalized airflow outside the diagnostic limits. The normalized airflow is derived by dividing the reference
(expected) airflow by the actual airflow. This normalized value is compared to the calibration values for the given
engineconditions.

Appendix
Appendix-8
11. Turbocharger Vane Control Position Sensor
The Turbocharger position sensor outputs a voltage corresponding to the turbo vane position. The output voltage is
measured and converted to a percent position by the ECM. The vane position will vary to achieve desired boost
levels dependent upon engine load and RPM.
Circuit Continuity Checks
Detects Turbocharger position signals that have spent a predetermined period of time in an unrealistic region.
Turbocharger Vane Control Position Sensor Circuit Low Voltage - P2564
Detects sensor output below a calibration voltage. If condition exists for a calibration period of time the code will set.
This check is enabled when engine is running.
Turbocharger Vane Control Position Sensor Circuit High Voltage - P2565
Detects sensor output above a calibration voltage. If condition exists for a calibration period of time the code will set.
This check is enabled when engine is running.
Rationality Check
Turbocharger Vane Control Position Sensor Performance - P2563
Detects turbocharger vane positions that do not match desired vane positions. The difference between actual vane
position and desired position must be within a calibration window. If it is outside of this window for a calibration
period of time, the code will set.
Turbocharger Vane Control Position Not Learned - P003A
Confirms the validity of the position sensor readings when the vanes are being commanded open and then close. If
the open value or the close value is outside of their respective window, the code sets.
12. Turbocharger Vane Control Solenoid Circuit
This is the turbocharger vane positioning solenoid, which is controlled by modulating its duty cycle.
Turbocharger Vane Control Solenoid Control Circuit - P0045
Detects opens and shorts on the vane positioning solenoid circuit. If during vane positioning the current is out of a
realistic range the code sets.
13. Glow Plug Control Module and Glow Plugs
a. Glow Plug Control Module Performance - P064C
This diagnosis determines if a failure occurred in the glow plug control module. The ECM receives
a message from the Glow Plug Control Module confirming the existence of any of the following
conditions: supply voltage not connected, glow plug switch is turned off because of overheat, glow
plug switch is defective (open or shorted) or voltage sensed by the glow plug control module is too
high or too low, ROM/RAM errors exist in GPCM.
b. Glow Plug Control Circuit - P0671, P0672, P0673, P0674, P0675, P0676, P0677, P0678
This diagnosis determines if a failure occurred on any of the glow plugs. The ECM receives the
message from the Glow Plug Control Module with the status of each glow plug. The status can be:
no fault, open or shorted as well as an increase or decrease in resistance detected. If the message
received indicates an error for a calibration time, code is set.
c. Lost Communications with Glow Plug Control Module - U0106
Detect failures with plug control module system messages sent from the GPCM to the ECM via the
GMLAN bus. If any expected messages are not received, then a CAN bus error exists. If the
absence of messages is inside the diagnostic's window then a malfunction is indicated.

Appendix
Appendix-9
14. Memory (ROM/RAM)
The ECM Read Only Memory stores the operational software and calibrations. The memory contents of ROM are
maintained even when the ignition is not on and/or the battery terminals are disconnected. The ECM's Random
Access Memory maintains software data during ECM operation. The contents of RAM are retained only with the
presence of battery connection and ignition on.
Control Module Not Programmed - P0602
The intent of this diagnostic is to indicate when a "no-run" calibration is programmed in the ECM. All ECM service
parts are delivered with a calibration that allows the module to be secured but does not allow the engine to run. When
this particular calibration is installed in the module, this fault code is set to indicate to service technicians that the
correct production calibration still needs to be programmed.
Control Module Internal Performance - P0606
The intent of this diagnostic is to detect malfunctions within the ECM. Read Only Memory (ROM) is checked by
performing a checksum of the contents of all programmed ROM memory parts (operational software and
calibrations). This checksum is calculated after every ECM power-up and compared to the imbedded checksums
within each software and calibration part. Random Access Memory (RAM) is checked by performing a read and write
sequence on every byte of RAM during ECM initialization. If the data being read back is not equivalent to the data
that was written, the diagnostic is set.
15. Malfunction Indicator (MIL) Lamp
Malfunction Indicator Lamp (MIL) Control Circuit - P0650
Electronic output driver circuitry checks for faults (open/short and no load) on the MIL circuit.
The ECM must be commanding the MIL on during a bulb check or DTC activation for the check to run.
16. Wait To Start (WTS) Lamp
Wait to Start Lamp (WTS) Control Circuit - P0381
Electronic output driver circuitry checks for faults (open/short and no load) on the WTS circuit.
The ECM must be commanding the WTS on during a bulb check or glow plug operation for the check to run.
17. ECM - TCM Communications
Lost communications with Transmission Control System - U0101
Detects loss of communication with the TCM resulting from GMLAN buss errors (opens/shorts)

Appendix
Appendix-10
18. Vehicle Speed Sensor
The vehicle output speed sensor contains a permanent magnet surrounded by a coil that gives off a continuous
magnetic field. As the vehicle is driven forward, a speed sensor rotor located near the magnetic pickup of the speed
sensor coil also rotates. This rotation produces a variable voltage signal in the pickup coil that is proportional to
vehicle speed. On a manual transmission this signal is sent directly to the ECM. On an automatic transmission the
speed signal is sent to the Transmission Control Module (TCM), which then sends a replicated version of the signal
to the ECM. The ECM uses this information to calculate actual vehicle speed and supply speed information to the
cluster and anti-lock brake module. The ECM also uses this information to calculate gear information for manual
transmission vehicles.
ManualTransmission
Vehicle Speed Sensor (VSS) Absence of Signal - P0502
Detects the absence of input signal from the VSS for a calibration amount of time, under conditions of engine torque
and speed that would indicate a signal should be present.
AutomaticTransmission
Diagnosed by the TCM

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