Possible Causes

Resistance difference between RCM housing ground and terminal ground could be caused by improper seating of RCM mounting bolts, incorrect tightening torque of RCM mounting bolts or high resistance in RCM logic ground circuit 31-JA10A (Black/Red wire).

1. Check for hard or intermittent DTC
   
   Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). See USING SCAN TOOL  under DIAGNOSTICS. Turn ignition switch to RUN position. Retrieve and record any continuous DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES (DTCS)  under DIAGNOSTICS. Perform on-demand self-test. See ON-DEMAND SELF-TEST  under DIAGNOSTICS. If DTC B1921 was retrieved during on-demand self-test, fault is hard. Go to next step. If DTC B1921 was not retrieved, fault is intermittent. Go to step  6 .
2. Check mounting of RCM
   
   Remove RCM. See RESTRAINTS CONTROL MODULE (RCM)  under REMOVAL & INSTALLATION. Inspect RCM mounting bracket and mounting surface for damage, corrosion or dirt. Ensure RCM mounting bolts are fully seated and properly tightened. See TORQUE SPECIFICATIONS  . If RCM mounting bolts are fully seated and tightened properly and no damage, corrosion or dirt is present, go to next step. If any damage or corrosion is found, clean, tighten bolts, and/or repair/replace as necessary. Go to step  7 .
3. Check RCM connector
   
   Ensure both RCM connectors are fully connected to RCM and Red locking tabs are engaged. If RCM connectors are connected correctly, go to next step. If RCM connectors are not connected correctly or locking tabs are not engaged, connect and engage as necessary and go to step  7 .
4. Check chassis ground
   
   Measure resistance between a known-good ground and RCM mounting surface. If resistance is more than 100 ohms, repair grounding system. Go to step  7 . If resistance is less than 100 ohms, go to next step.
5. Check for ground circuit open
   
   Turn ignition switch to OFF position. Measure resistance between sheet metal ground near RCM and RCM connector C310A, terminal No. 21 (Black/Red wire). See Figure . If resistance is more than 100 ohms, repair open in Black/Red wire. See WIRING DIAGRAMS  . Go to step  7 . If resistance is less than 100 ohms, replace RCM. Go to step  7 .
6. Check for intermittent fault
   
   Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Perform on-demand self-test. If DTC B1921 was retrieved during on-demand self-test, go to step  2 . If DTC B1921 was not retrieved during on-demand self-test, check for cause of intermittent high resistance in Black/Red wire. See WIRING DIAGRAMS  . Attempt to recreate fault by flexing wire harness and cycling ignition switch frequently. Repair any intermittent problems found. Go to next step.
7. Check for additional DTCs
   
   Refer to continuous DTCs recorded in step  1 . If any continuous DTCs were retrieved, go to diagnostic trouble code identification table for direction to appropriate test. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION  table. DO NOT clear any DTCs until all DTCs have been resolved. If no continuous DTCs were retrieved, reconnect air bag system. Activate air bag system. See ACTIVATING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Clear all DTCs. See CLEARING FAULT CODES  under DIAGNOSTICS.