Data Communications (U2142 and U2143 only)
DTC U2105-U2199 (U2142 and U2143 only)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC U2142 00
- Lost Communication With Yaw Rate Sensor (YRS)
DTC U2143 00
- Lost Communication with Steering Wheel Angle Sensor
Diagnostic Fault Information
Circuit/System Description
The electronic brake control module (EBCM) activates the other control modules connected to the CAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The EBCM, Yaw and Lateral Accelerometer Sensor, and Steering Angle Sensor are the only control modules connected to the CAN bus serial data circuits.
Conditions for Running the DTC
* The system voltage is between 9-16 V.
* The vehicle power mode master requires serial data communication to occur.
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
* The vehicle stability enhancement system (VSES), if equipped, and traction control system (TCS) will not function.
* System OFF lamps will illuminate for these systems.
Conditions for Clearing the DTC
* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the 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 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.
* 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.
Reference Information
Schematic Reference
* Data Communication Schematics [1][2]Electrical Diagrams
* Antilock Brake System Schematics [1][2]Antilock Brakes / Traction Control Systems
* Control Module References Control Module References
Connector End View Reference
Component Connector End Views Folding Top 5 Bow Lowered Switch (CM7)
Description and Operation
ABS Description and Operation Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify that DTC U2142 and U2143 are not set in electronic brake control module.
• If only DTC U2142 is set
Refer to Circuit/System Testing - Only DTC U2142 is set
• If only DTC U2143 is set
Refer to Circuit/System Testing - Only DTC U2143 is set
• If both DTC U2142 and U2143 are set
Refer to Circuit/System Testing - Both DTC U2142 and U2143 are set
3. All OK
Circuit/System Testing
Only DTC U2142 is set
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the yaw and lateral accelerometer sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 1 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the ground circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the ignition circuit terminal 4 and ground.
• If the test lamp does not illuminate
Repair the open/high resistance in the ignition circuit between the X3 fuse block connector and the yaw and lateral accelerometer sensor.
• If the test lamp illuminates
5. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
6. Test for less than 130 ohms between the serial data circuits terminal 2 and 3.
• If 130 ohms or greater
Repair the open/high resistance in the circuits between the inline connectors and the yaw and lateral accelerometer sensor.
• If less than 130 ohms
7. Replace the yaw and lateral accelerometer sensor.
Only DTC U2143 is set
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the steering angle sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the ground circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the ignition circuit terminal 5 and ground.
• If the test lamp does not illuminate
Repair the open/high resistance in the ignition circuit between the X3 fuse block connector and the steering angle sensor.
• If the test lamp illuminates
5. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
6. Test for less than 70 ohms between the serial data circuits terminal 1 and 3.
• If 70 ohms or greater
Repair the open/high resistance in the circuits between the inline connectors and the steering angle sensor.
• If less than 70 ohms
7. Replace the steering angle sensor.
Both DTC U2142 and U2143 are set
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the steering angle sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the ground circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the ignition circuit terminal 5 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
2. Test for less than 2 ohms in the ignition circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
2. Test for greater than 100 ohms between the ignition circuit and ground.
• If greater than 100 ohms, replace the steering angle sensor.
• If 100 ohms or less
Note: The suspension control switch is only available for ZR1.
3. Disconnect the harness connector at the yaw and lateral accelerometer sensor and suspension control switch.
4. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the yaw and lateral accelerometer sensor.
• If the test lamp illuminates
5. Test for less than 4.5 V between each serial data circuits listed below and ground.
* Terminal 1
* Terminal 3
• If 4.5 V or greater
1. Ignition OFF, disconnect the harness connectors at the yaw and lateral accelerometer sensor, ignition ON.
2. Test for less than 4.5 V between the serial data circuit and ground.
• If 4.5 V or less, replace the yaw and lateral accelerometer sensor.
• If greater than 4.5 V
3. Ignition OFF, disconnect the harness connectors at the electronic brake control module, ignition ON.
4. Test for less than 1 V between the serial data circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the electronic brake control module.
• If less than 4.5 V
6. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
7. Test for greater than 100 ohms between each serial data circuits listed below and ground.
* Terminal 1
* Terminal 3
• If 100 ohms or less
1. Ignition OFF, disconnect the harness connectors at the electronic brake control module.
2. Test for greater than 100 ohms between the serial data circuit and ground.
• If 100 ohms or greater, replace the electronic brake control module.
• If less than 100 ohms
3. Disconnect the harness connectors at the yaw and lateral accelerometer sensor.
4. Test for infinite resistance between the serial data circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the yaw and lateral accelerometer sensor.
• If greater than 100 ohms
8. Test for 50-70 ohms between the serial data circuits terminal 1 and 3.
• If less than 50 ohms
1. Ignition OFF, disconnect the harness connectors at the electronic brake control module.
2. Test for greater than 110 ohms between the serial data circuits.
• If 110 ohms or greater, replace the electronic brake control module.
• If less than 110 ohms
3. Disconnect the harness connectors at the yaw and lateral accelerometer sensor.
4. Test for infinite resistance between the serial data circuits.
• If less than infinite resistance, repair the short between the circuits.
• If infinite resistance, replace the yaw and lateral accelerometer sensor.
• If greater than 70 ohms
1. Ignition OFF, disconnect the harness connectors at the electronic brake control module.
2. Test for less than 2 ohms in the serial data circuits listed below end to end.
* The steering angle sensor terminal 1 and the electronic brake control module terminal 24
* The steering angle sensor terminal 3 and the electronic brake control module terminal 37
• If greater than 2 ohms, repair the open/high resistance in the circuit.
• If less than 2 ohms
3. Test for less than 130 ohms between the serial data circuits terminal 1 and 3.
• If 130 ohms or less, replace the electronic brake control module.
• If greater than 130 ohms
4. Disconnect the harness connectors at the yaw and lateral accelerometer sensor.
5. Test for less than 2 ohms in the serial data circuits listed below end to end.
* The steering angle sensor terminal 1 and the yaw and lateral accelerometer sensor terminal 2
* The steering angle sensor terminal 3 and the yaw and lateral accelerometer sensor terminal 3
• If greater than 2 ohms, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the yaw and lateral accelerometer sensor.
• If between 50-70 ohms
9. Replace the steering angle sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* GMLAN Wiring Repairs GMLAN Wiring Repairs
* Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement Service and Repair
* Control Module References Control Module References for control module replacement, programming and setup