Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Grand Marquis and 2006 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 indicator and the secondary air bag warning chime will be activated.