Test D: LFC 21/DTC B1921-RCM Bracket Ground Resistance Hi

D1:

D2 - D4:

D5 - D6:

D7 - D8:

D9 - D10:

Normal Operation

WARNING: THE TIGHTENING TORQUE OF THE AIR BAG ELECTRONIC CRASH SENSOR (ECS) MODULE RETAINING BOLTS IS CRITICAL FOR PROPER AIR BAG SUPPLEMENTAL RESTRAINT SYSTEM (SRS) OPERATION. REFER TO MODULE AIR BAG ELECTRONIC CRASH SENSOR (ECS) IN THIS SECTION FOR PROPER TORQUE VALUES.

The air bag Electronic Crash Sensor (ECS) module monitors the resistance between the ground connections at its housing and the reference ground at Pins 21 and 22. If the ECS detects a resistance greater than 100 ohms, it will store a Diagnostic Trouble Code (DTC) B1921 in memory and flash a Lamp Fault Code (LFC) 21 (or higher priority code if one exists) on the air bag indicator.

Possible Causes
High resistance between the ECS module housing ground and pin ground could be caused by:
^ improper seating of the ECS module retaining bolts.
^ improper tightening torque of the ECS module retaining bolts.
^ high resistance on both ECS logic ground circuits 649 (BK/O).