B1921

DTC B1921 / LFC 21 - GROUND RESISTANCE TOO HIGH OR THE RESTRAINTS CONTROL MODULE NOT MOUNTED TO THE VEHICLE PROPERLY

Normal Operation

WARNING: The tightening torque of the restraints control module (RCM) retaining bolts is critical for proper air bag system operation.

See RESTRAINTS CONTROL MODULE REMOVAL/INSTALLATION for proper torque values.

The restraints control module (RCM) monitors the resistance between the ground connections at its housing and the reference ground at pin 21. If the RCM 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 RCM housing ground and pin ground could be caused by:
- improper seating of the RCM retaining bolts.
- improper tightening torque of the RCM retaining bolts.
- wiring, terminals, or connectors.

WARNING: If the supplemental restraint system (SRS) is being serviced, the system must be deactivated and restraint system diagnostic tools must be installed.

The air bag restraint system diagnostic tools must be removed and the air bag modules reconnected when the system is reactivated to avoid non-deployment in a collision, resulting in possible personal injury.

WARNING: Never probe the connectors on the air bag module. Doing so can result in air bag deployment, which can result in personal injury.

WARNING: The safety belt pretensioner is a pyrotechnic device. Always wear safety glasses when repairing an air bag equipped vehicle and when handling a safety belt buckle pretensioner or safety belt retractor pretensioner.

Never probe a pretensioner electrical connector. Doing so could result in pretensioner or air bag deployment and could result in personal injury.

NOTE: After diagnosing or repairing an SRS, the restraint system diagnostic tools must be removed before operating the vehicle over the road.

NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer

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