2010 Cadillac Truck Escalade RWD V8-6.2L Page 2769
U0209
DTC U0100-U02FF (without HP2)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
Refer to Control Module U Code List (See: Diagnostic Trouble Code Descriptions/Control Module U Code List).
Diagnostic Fault Information
Circuit/System Description
The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the
serial data circuit through the DLC, the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic
trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health
(SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for
example if the module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on
the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the
loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more
control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that
contain the stored code.
Conditions for Running the DTC
The system voltage is between 9-16 V.
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
* Specific subsystems will not function.
* DTC U0100 in the TCM will cause the transmission to go into default gears.
* Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.
Conditions for Clearing the DTC
* The ECM/TCM turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Saturday, August 1, 2020
2010 Cadillac Truck SRX AWD V6-3.0L Page 1301
2010 Cadillac Truck SRX AWD V6-3.0L Page 1301
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P219A
- Air Fuel Imbalance Bank 1
DTC P219B
- Air Fuel Imbalance Bank 2
Circuit/System Description
The Air Fuel Imbalance diagnostic detects a rich or lean cylinder to cylinder air/fuel ratio imbalance in each bank. The diagnostic monitors the
pre-catalyst heated oxygen sensor (HO2S) signal's frequency and amplitude characteristics by calculating an accumulated voltage over a
predetermined sample period. An imbalance is indicated when multiple samples of the accumulated voltage are consistently higher than the desired
value.
Conditions for Running the DTC
* DTCs P0053, P0059, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0125, P0128, P0131, P0132, P0133,
P0134, P0135, P0151, P0152, P0153, P0154, P0155, P0178, P0179, P0201-P0208, P0300, P0301-P0308, P0411, P0442, P0443, P0446,
P0449, P0452, P0453, P0455, P0496, P0606, P1133, P1153, P1516, P2101, P2135, P2176, P2269, P2440, P2444, P2A00, P2A03 are not set.
* The device control is not active.
* The intrusive diagnostics are not active.
* The engine overspeed protection is not active.
* Reduced power mode, ETC DTC, is not active.
* The power take-off (PTO) is not active.
* The traction control is not active.
* The fuel control is in air-fuel Closed Loop.
* The system voltage is more than 10 V, or less than 18 V.
* The engine coolant temperature (ECT) is warmer than -20掳C (-4掳F).
* The engine speed is greater than 350 RPM, but less than 6,000 RPM.
* The mass air flow is greater than 11 g/s, but less than 510 g/s.
* Percent ethanol is less than 87 %.
Conditions for Setting the DTC
Multiple samples of the pre-catalyst HO2S accumulated voltage are consistently greater than the desired value.
Action Taken When the DTC Sets
DTCs P219A and P219B are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P219A and P219B are Type B DTCs.
Diagnostic Aids
* The air fuel imbalance diagnostic is very sensitive to heated oxygen sensor (HO2S) design. A non-OE sensor or an incorrect part number
may set a false DTC.
* Monitoring the misfire current counters, or misfire graph, may help to isolate the cylinder that is causing the condition.
Reference Information
Schematic Reference
Engine Controls Schematics (LAU) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)Engine Controls Schematics
(LF1) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views/Connector End Views By Name)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Troubleshooting with a Test Lamp (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Circuit Testing/Troubleshooting with a Test Lamp)
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2768
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2768
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Verify that DTC U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.
If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic
Trouble Code (DTC) List - Vehicle).
Circuit/System Testing
Note: Use the schematic to identify the following:
* Control modules the vehicle is equipped with
* Control module locations on the low and high speed GMLAN serial data circuits
* The control modules B+, ignition, ground, communication enable and serial data circuit terminals
1. Determine the control module that is not communicating. Refer to Control Module U Code List (See: Diagnostic Trouble Code
Descriptions/Control Module U Code List).
2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
3. Test for less than 10 ohm between each ground circuit terminal and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the
control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
5. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test
the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
Note: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit,
and the BCM is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits.
6. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup
circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
7. Ignition OFF for 60 seconds, test for less than 5 ohm between the serial data circuit terminals and the appropriate DLC terminal listed below:
* Class 2 serial data circuit terminal 2
* Low speed GMLAN serial data terminal 1
* High speed GMLAN serial data terminal 6 or 14
瀚慖f greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module
and a control module setting the DTC or a serial data splice pack.
8. If all circuits test normal, replace the control module that is not communicating.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* GMLAN Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Wiring Repairs/GMLAN Wiring Repairs)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for control module replacement, setup, and
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Verify that DTC U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.
If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic
Trouble Code (DTC) List - Vehicle).
Circuit/System Testing
Note: Use the schematic to identify the following:
* Control modules the vehicle is equipped with
* Control module locations on the low and high speed GMLAN serial data circuits
* The control modules B+, ignition, ground, communication enable and serial data circuit terminals
1. Determine the control module that is not communicating. Refer to Control Module U Code List (See: Diagnostic Trouble Code
Descriptions/Control Module U Code List).
2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
3. Test for less than 10 ohm between each ground circuit terminal and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the
control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
5. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test
the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
Note: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit,
and the BCM is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits.
6. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup
circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
7. Ignition OFF for 60 seconds, test for less than 5 ohm between the serial data circuit terminals and the appropriate DLC terminal listed below:
* Class 2 serial data circuit terminal 2
* Low speed GMLAN serial data terminal 1
* High speed GMLAN serial data terminal 6 or 14
瀚慖f greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module
and a control module setting the DTC or a serial data splice pack.
8. If all circuits test normal, replace the control module that is not communicating.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* GMLAN Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Wiring Repairs/GMLAN Wiring Repairs)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for control module replacement, setup, and
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2767
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2767
control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that
contain the stored code.
Conditions for Running the DTC
The system voltage is between 9-16 V.
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
* Specific subsystems will not function.
* DTC U0100 in the TCM will cause the transmission to go into default gears.
* Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.
Conditions for Clearing the DTC
* The ECM/TCM turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Diagnostic Aids
* Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no
associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are
transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically
after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios:
- A control module on the data communication circuit was disconnected while the communication circuit is awake.
- Power to one or more control modules was interrupted during diagnosis.
- A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold.
- Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time.
- If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above.
These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
* A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between
control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a
control module based only on a history U-code.
* Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication
issue.
* Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system
inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
* Use Data Link References (See: Powertrain Management/Computers and Control Systems/Information Bus/Testing and Inspection/Initial
Inspection and Diagnostic Overview) to determine if the control module uses high or low speed GMLAN serial data communications.
* Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and
the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control
module.
* This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to,
providing the vehicle is equipped with the control module.
Reference Information
Schematic Reference
* Data Communication Schematics (See: Powertrain Management/Computers and Control Systems/Information Bus/Diagrams/Electrical
Diagrams)
* Control Module References (See: Testing and Inspection/Programming and Relearning)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Data Link Communications Description and Operation (See: Powertrain Management/Computers and Control Systems/Information
Bus/Description and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that
contain the stored code.
Conditions for Running the DTC
The system voltage is between 9-16 V.
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
* Specific subsystems will not function.
* DTC U0100 in the TCM will cause the transmission to go into default gears.
* Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.
Conditions for Clearing the DTC
* The ECM/TCM turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Diagnostic Aids
* Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no
associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are
transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically
after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios:
- A control module on the data communication circuit was disconnected while the communication circuit is awake.
- Power to one or more control modules was interrupted during diagnosis.
- A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold.
- Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time.
- If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above.
These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
* A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between
control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a
control module based only on a history U-code.
* Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication
issue.
* Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system
inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
* Use Data Link References (See: Powertrain Management/Computers and Control Systems/Information Bus/Testing and Inspection/Initial
Inspection and Diagnostic Overview) to determine if the control module uses high or low speed GMLAN serial data communications.
* Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and
the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control
module.
* This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to,
providing the vehicle is equipped with the control module.
Reference Information
Schematic Reference
* Data Communication Schematics (See: Powertrain Management/Computers and Control Systems/Information Bus/Diagrams/Electrical
Diagrams)
* Control Module References (See: Testing and Inspection/Programming and Relearning)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Data Link Communications Description and Operation (See: Powertrain Management/Computers and Control Systems/Information
Bus/Description and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
2010 Cadillac CTS Sedan AWD V6-3.0L Technical Service Bulletin # 08-06-01-008A Date: 090727
2010 Cadillac CTS Sedan AWD V6-3.0L Technical Service Bulletin # 08-06-01-008A Date: 090727
Engine - Drive Belt Misalignment Diagnostics
INFORMATION
Bulletin No.: 08-06-01-008A
Date: July 27, 2009
Subject: Diagnosing Accessory Drive Belt / Serpentine Belt Noise and Availability and Use of Kent-Moore EN-49228 Laser Alignment Tool -
Drive Belt
Models:
2010 and Prior GM Passenger Cars and Trucks (Including Saturn)
2010 and Prior HUMMER H2, H3 Vehicles
2009 and Prior Saab 9-7X
Supercede:
This bulletin is being revised to add a model year and update the Tool Information. Please discard Corporate Bulletin Number 08-06-01-008
(Section 06 - Engine).
Background
Several aftermarket companies offer laser alignment tools for accessory drive systems that can be very helpful in eliminating drive belt noise as a
result of misaligned pulleys. Typically pricing ranges from $160 - $200.
EN-49228 Laser Alignment Tool - Drive Belt
The GM Tool program has now made available a competitive, simple to use and time-saving laser tool to assist in achieving precise alignment of
the drive belt pulleys. This optional tool removes the guesswork from proper pulley alignment and may serve to reduce comebacks from:
- Drive Belt Noise
- Accelerated Drive Belt Wear
- Drive Belt Slippage
Instructions
The instructions below are specific only to the truck Gen IV V-8 family of engines. These instructions are only for illustrative purposes to show
how the tool may be used. Universal instructions are included in the box with the Laser Alignment Tool - Drive Belt.
Caution
- Do not look directly into the beam projected from the laser.
2010 Cadillac CTS Sedan AWD V6-3.0L Page 188
- Use caution when shining the laser on highly polished or reflective surfaces. Laser safety glasses help reduce laser beam glare in many
circumstances.
- Always use laser safety glasses when using the laser. Laser safety glasses are not designed to protect eyes from direct laser exposure.
1. Observe and mark the serpentine belt orientation.
2. Remove the serpentine belt from the accessory drive system.
3. Install the tool onto the power steering pulley. Position the legs of the tool into the outer grooves of the pulley, farthest from the front of the
engine.
4. Install the retaining cord around the pulley and to the legs of the tool.
5. Put on the laser safety glasses provided with the tool.
6. Depress the switch on the rear of the tool to activate the light beam.
7. Rotate the power steering pulley as required to project the light beam onto the crankshaft balancer pulley grooves.
8. Inspect for proper power steering pulley alignment.
- If the laser beam projects onto the second rib or raised area (1), the pulleys are aligned properly.
- If the laser beam projects more than one-quarter rib 0.9 mm (0.035 in) mis-alignment, adjust the position of the power steering pulley as
required.
2010 Cadillac CTS Sedan AWD V6-3.0L Page 189
- Refer to SI for Power Steering Pulley Removal and Installation procedures.
9. Install the serpentine belt to the accessory drive system in the original orientation.
10. Operate the vehicle and verify that the belt noise concern is no longer present.
Tool Information
Please visit the GM service tool website for pricing information or to place your order for this tool.
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2766
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2766
6. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup
circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
7. Ignition OFF for 60 seconds, test for less than 5 ohm between the serial data circuit terminals and the appropriate DLC terminal listed below:
* Class 2 serial data circuit terminal 2
* Low speed GMLAN serial data terminal 1
* High speed GMLAN serial data terminal 6 or 14
瀚慖f greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module
and a control module setting the DTC or a serial data splice pack.
8. If all circuits test normal, replace the control module that is not communicating.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* GMLAN Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Wiring Repairs/GMLAN Wiring Repairs)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for control module replacement, setup, and
programming
U0208
DTC U0100-U02FF (without HP2)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
Refer to Control Module U Code List (See: Diagnostic Trouble Code Descriptions/Control Module U Code List).
Diagnostic Fault Information
Circuit/System Description
The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the
serial data circuit through the DLC, the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic
trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health
(SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for
example if the module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on
the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the
loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more
6. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup
circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
7. Ignition OFF for 60 seconds, test for less than 5 ohm between the serial data circuit terminals and the appropriate DLC terminal listed below:
* Class 2 serial data circuit terminal 2
* Low speed GMLAN serial data terminal 1
* High speed GMLAN serial data terminal 6 or 14
瀚慖f greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module
and a control module setting the DTC or a serial data splice pack.
8. If all circuits test normal, replace the control module that is not communicating.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* GMLAN Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Wiring Repairs/GMLAN Wiring Repairs)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for control module replacement, setup, and
programming
U0208
DTC U0100-U02FF (without HP2)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
Refer to Control Module U Code List (See: Diagnostic Trouble Code Descriptions/Control Module U Code List).
Diagnostic Fault Information
Circuit/System Description
The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the
serial data circuit through the DLC, the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic
trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health
(SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for
example if the module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on
the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the
loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2765
2010 Cadillac Truck Escalade RWD V8-6.2L Page 2765
* Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and
the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control
module.
* This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to,
providing the vehicle is equipped with the control module.
Reference Information
Schematic Reference
* Data Communication Schematics (See: Powertrain Management/Computers and Control Systems/Information Bus/Diagrams/Electrical
Diagrams)
* Control Module References (See: Testing and Inspection/Programming and Relearning)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Data Link Communications Description and Operation (See: Powertrain Management/Computers and Control Systems/Information
Bus/Description and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Verify that DTC U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.
If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic
Trouble Code (DTC) List - Vehicle).
Circuit/System Testing
Note: Use the schematic to identify the following:
* Control modules the vehicle is equipped with
* Control module locations on the low and high speed GMLAN serial data circuits
* The control modules B+, ignition, ground, communication enable and serial data circuit terminals
1. Determine the control module that is not communicating. Refer to Control Module U Code List (See: Diagnostic Trouble Code
Descriptions/Control Module U Code List).
2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
3. Test for less than 10 ohm between each ground circuit terminal and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the
control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
5. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test
the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
Note: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit,
and the BCM is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits.
* Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and
the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control
module.
* This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to,
providing the vehicle is equipped with the control module.
Reference Information
Schematic Reference
* Data Communication Schematics (See: Powertrain Management/Computers and Control Systems/Information Bus/Diagrams/Electrical
Diagrams)
* Control Module References (See: Testing and Inspection/Programming and Relearning)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Data Link Communications Description and Operation (See: Powertrain Management/Computers and Control Systems/Information
Bus/Description and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Verify that DTC U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.
If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic
Trouble Code (DTC) List - Vehicle).
Circuit/System Testing
Note: Use the schematic to identify the following:
* Control modules the vehicle is equipped with
* Control module locations on the low and high speed GMLAN serial data circuits
* The control modules B+, ignition, ground, communication enable and serial data circuit terminals
1. Determine the control module that is not communicating. Refer to Control Module U Code List (See: Diagnostic Trouble Code
Descriptions/Control Module U Code List).
2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
3. Test for less than 10 ohm between each ground circuit terminal and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the
control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
5. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
瀚慖f the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test
the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
Note: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit,
and the BCM is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits.
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