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 2 (CAN2) bus. If the RCM  detects a fault with communications with the ABS module or CAN2 bus circuits, it will set DTC U0028:08 or U0028:88.

The RCM  does not request the Instrument Cluster (IC) module 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 CAN2 bus messages from the ABS module for 5 seconds, a fault will be indicated. An open CAN2 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 CAN2 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