Test C: LFC 21/DTC B1921 - Ground Resistance Too Hi or the ECS Module Not Mounted to the Vehicle Correctly
C1 - C2
C2 - C4
C5 - C7
C7 - C9
C10
Normal Operation
WARNING: THE TIGHTENING TORQUE OF THE AIR BAG ELECTRONIC CRASH SENSOR (ECS) MODULE RETAINING BOLTS IS CRITICAL FOR CORRECT AIR BAG SUPPLEMENTAL RESTRAINT SYSTEM (SRS) OPERATION. REFER TO AIR BAG CONTROL MODULE FOR CORRECT 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:
incorrect seating of the ECS module retaining bolts.
incorrect tightening torque of the ECS module retaining bolts.
high resistance on both ECS logic ground circuits 57 (BK).
