Normal Operation and Fault Conditions: Notes

The RCM continuously monitors the driver airbag stage 1 circuits for the following faults:

• Resistance out of range
• Unexpected voltage
• Short to ground
• Faulted driver airbag

If a fault is detected, the RCM stores DTC B0001:11, B0001:12, B0001:13 or B0001:1A in memory and sends a message to the IPC to illuminate the airbag warning indicator.

The RCM analyzes the deployment loop resistance to determine if a fault exists. The value displayed in the Parameter Identification (PID) is the deployment loop resistance measured by the RCM. If the value displayed is lower or higher than the desired range (refer to diagram below in Fig 1), the RCM can set a DTC. As the deployment loop resistance drifts farther outside the desired range, the chance for a DTC increases. Small variations in resistance can occur due to the effect of road vibrations on terminal fit. Crimps and terminals can be affected by stress and harness movement and can cause an increase in resistance due to wire strain. These variables can result in an intermittent fault. For this reason, the test requires the Parameter Identification (PID) value to be within the desired range before the fault is considered repaired, regardless if the module is reporting an on-demand DTC at the time of diagnosis. Following this direction helps make sure that minor changes in resistance do not create a repeat concern. This test uses process of elimination to diagnose each part of the deployment loop circuit including:

• Wiring
• Connections
• Clockspring
• Driver airbag
• RCM

Fig 1: Restraints Control Module - Loop Circuit

Courtesy of FORD MOTOR CO.