U2143

DTC U2105-U2199

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC U2142 00
- Lost Communication With Yaw Rate Sensor (YRS)

DTC U2143 00
- Lost Communication With Steering Angle Sensor (SAS)




Circuit/System Description

Modules connected to the CAN bus serial data circuits are high speed serial data modules that monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.


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 volts.
* 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

* Use the DTC Descriptor list above to determine the module which is not communicating.
* If there are multiple non-communicating modules choose the one closest to the EBCM.



Reference Information
Schematic Reference

* Data Communication Schematics (Electrical Diagrams)
* Antilock Brake System Schematics ([1][2]Antilock Brakes / Traction Control Systems)
* Control Module References (Programming and Relearning)

Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Data Link Communications Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Testing

1. Using the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
2. Ignition OFF, disconnect the harness connector of the module that is not communicating.
3. Ignition ON, verify that a test lamp illuminates between the module voltage circuit and ground.

• If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM.

4. Test for less than 5 ohm of resistance between the module ground circuits and ground.

• If greater than 5 ohm, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.

5. If all circuits test normal, replace the module that is not communicating.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* GMLAN Wiring Repairs (Component Tests and General Diagnostics)
* Control Module References (Programming and Relearning) for module replacement, setup, and programming