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U2140




DTC U2105-U2199

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 C0710 00
- Steering Position Signal

DTC C0710 5A
- Steering Position Signal Plausibility Failure

Diagnostic Fault Information





Circuit/System Description

The electronic brake control module (EBCM) activates the other modules connected to the CAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The EBCM, Yaw Rate Sensor, and the Steering Angle Sensor are the only modules connected to the CAN bus serial data circuits. For more information on CAN bus serial data refer to Data Link Communications Description and Operation (Description and Operation).

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.
* 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 to determine if the 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 (Electrical Diagrams)
* Antilock Brake System Schematics (Electrical Diagrams)
* Control Module References (Programming and Relearning)

Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning)for scan tool information

Circuit/System Verification

1. Ignition ON.
2. Verify that DTC C0710 and U2142 are not set.

If only DTC C0710 is set
Refer to Circuit/System Testing - Only DTC C0710 is set

If only DTC U2142 is set
Refer to Circuit/System Testing - Only DTC U2142 is set

If both DTC C0710 and U2142 are set
Refer to Circuit/System Testing - Both DTC C0710 and U2142 are set

3. All OK

Circuit/System Testing

Only DTC C0710 is set
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the steering wheel speed position sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohm between the low reference circuit terminal 6 and ground.

If 10 ohm or greater
Repair the open/high resistance in the circuit between the X201 inline connector and the steering wheel speed position sensor.

If less than 10 ohm

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 circuit between the X201 inline connector and the steering wheel speed position 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 ohm between the serial data circuits terminal 2 and 3.

If 70 ohm or greater
Repair the open/high resistance in the circuits between the X201 inline connector and the steering wheel speed position sensor.

If less than 70 ohm

7. Replace the steering wheel speed position sensor.

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 ohm between the low reference circuit terminal 1 and ground.

If 10 ohm or greater
Repair the open/high resistance in the circuit between the X201 inline connector and the yaw and lateral accelerometer sensor.

If less than 10 ohm

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 circuit between the X201 inline 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 ohm between the serial data circuits terminal 2 and 3.

If 130 ohm or greater
Repair the open/high resistance in the circuits between the X201 inline connector and the yaw and lateral accelerometer sensor.

If less than 130 ohm

7. Replace the yaw and lateral accelerometer sensor.

Both DTC C0710 and U2142 are set
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the steering wheel speed position sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohm between the low reference circuit terminal 6 and ground.

If 10 ohm or greater

1. Ignition OFF, disconnect the harness connector at the electronic brake control module.
2. Test for less than 2 ohm in the low reference circuit end to end.

If 2 ohm or greater, repair the open/high resistance in the circuit between the splice and the electronic brake control module.
If less than 2 ohm, replace the electronic brake control module.

If less than 10 ohm

3. Ignition ON.
4. Verify a test lamp illuminates between the ignition circuit terminal 5 and ground.

If the test lamp does not illuminate

1. Ignition OFF, disconnect the harness connectors at the yaw and lateral accelerometer sensor, ignition ON.
2. Verify a test lamp illuminates between the ignition circuit and ground.

If the test lamp illuminates, replace the yaw and lateral accelerometer sensor.

If the test lamp does not illuminate

3. Ignition OFF, disconnect the harness connectors at the electronic brake control module.
4. Test for infinite resistance between the ignition circuit and ground.

If less than infinite resistance, repair the short ground on the circuit.

If infinite resistance

5. Test for less than 2 ohm in the ignition circuit end to end between the steering wheel speed position sensor and the electronic brake control module terminal 32.

If greater than 2 ohm, repair the open/high resistance in the circuit.
If less than 2 ohm, replace the electronic brake control module.

If the test lamp illuminates

5. Test for less than 4.5 V between the serial data circuits listed below and ground.

* Terminal 2
* 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 ohm between the serial data circuits listed below and ground.

* Terminal 2
* Terminal 3

If 100 ohm or less

1. Ignition OFF, disconnect the harness connectors at the electronic brake control module.
2. Test for greater than 100 ohm between the serial data circuit and ground.

If 100 ohm or greater, replace the electronic brake control module.

If less than 100 ohm

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 ohm

8. Test for 50-70 ohm between the serial data circuits terminal 2 and 3.

If less than 50 ohm

1. Ignition OFF, disconnect the harness connectors at the electronic brake control module.
2. Test for greater than 110 ohm between the serial data circuits.

If 110 ohm or greater, replace the electronic brake control module.

If less than 110 ohm

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 ohm

1. Ignition OFF, disconnect the harness connectors at the electronic brake control module.
2. Test for less than 2 ohm in the serial data circuits listed below end to end.

* The steering wheel speed position sensor terminal 2 and the electronic brake control module terminal 24
* The steering wheel speed position sensor terminal 3 and the electronic brake control module terminal 37

If greater than 2 ohm, repair the open/high resistance in the circuit.

If less than 2 ohm

3. Test for less than 130 ohm between the serial data circuits terminal 2 and 3.

If 130 ohm or less, replace the electronic brake control module.

If greater than 130 ohm

4. Disconnect the harness connectors at the yaw and lateral accelerometer sensor.
5. Test for less than 2 ohm in the serial data circuits listed below end to end.

* The steering wheel speed position sensor terminal 2 and the yaw and lateral accelerometer sensor terminal 2
* The steering wheel speed position sensor terminal 3 and the yaw and lateral accelerometer sensor terminal 3

If greater than 2 ohm, repair the open/high resistance in the circuit.
If less than 2 ohm, replace the yaw and lateral accelerometer sensor.

If between 50-70 ohm

9. Replace the steering wheel speed position 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)
* Steering Angle Sensor Replacement (Removal and Replacement)
* Control Module References (Programming and Relearning)for module replacement, programming and setup