Normal Operation
WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
The Restraints Control Module (RCM) monitors the resistance between the ground connections at the mounting bracket and the reference ground at the C310a Pin 16, circuit 676 (PK/OG).
If the RCM detects a difference in resistance, it will store DTC B1921 in memory, flash LFC 1-4 on the air bag warning indicator.
- DTC B1921 Air Bag Diagnostic Monitor Ground Circuit Open - If the RCM detects a difference in resistance between the ground circuit and the RCM mounting ground, it will set this DTC.
This pinpoint test is intended to diagnose the following:
- RCM bracket not securely mounted
- Wiring, terminals or connectors
- RCM