Normal Operation

The Restraints Control Module (RCM) supplies the stability/traction control system with the yaw rate, roll rate, lateral and longitudinal accelerometer over a dedicated Controller Area Network (CAN) bus. If the RCM detects a fault with communications with the ABS module or dedicated CAN bus circuits, it will set DTC U0028:08 or U0028:88.

The RCM does not request the Instrument Panel Cluster (IPC) to illuminate the air bag warning indicator if either DTC U0028:08 or U0028:88 is set.

• DTC U0028:08 (Vehicle Communication Bus A: Bus Signal / Message Failures) - When the RCM does not receive dedicated CAN bus messages from the ABS module for 5 seconds, a fault will be indicated. An open dedicated CAN circuit, incorrectly installed ABS module or loss of power and/or ground to the ABS module can set this DTC.
• DTC U0028:88 (Vehicle Communication Bus A: Bus Off) - When the RCM detects the dedicated CAN circuits are shorted to ground, shorted to voltage or shorted to each other, a fault will be indicated.

This pinpoint test is intended to diagnose the following: 

• Wiring, terminals or connectors
• RCM
• ABS module