Normal Operation
WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The Restraints Control Module (RCM) supplies the stability/traction control system with the yaw rate, roll rate, lateral and longitudinal accelerometer over a dedicated High Speed Controller Area Network (HS-CAN) bus. If the RCM detects a fault with communications with the ABS module or dedicated Controller Area Network (CAN) bus circuits, it sets 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 is indicated. An open circuit on the dedicated CAN bus, an 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 is indicated.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- RCM
- ABS module