Possible Causes

High resistance between RCM housing ground and terminal ground could be caused by improper tightening or seating of RCM mounting bolts, high resistance in RCM logic ground circuit or faulty RCM.

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 FAULT CODES  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
   
   Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Remove RCM. See RESTRAINTS CONTROL MODULE (RCM)  under REMOVAL & INSTALLATION. Inspect RCM, mounting bracket and mounting surface for damage or corrosion. Inspect RCM bracket bolts and ensure bolts are fully seated and tightened properly. If bracket and mounting surface is okay and mounting bolts are tight, go to next step. If bracket and mounting surface is not okay and/or mounting bolts are not tight, repair or replace as necessary. Go to step  7.
3. Check RCM harness connection
   
   Ensure RCM connector is fully connected. If RCM connector is fully connected, go to next step. If RCM connector is not fully connected, reconnect connector. Go to step  7.
4. Check vehicle chassis ground
   
   Measure resistance between a known good ground and RCM mounting surface. If resistance more than 100 ohms, repair grounding system. Go to step  7. If resistance is less than 100 ohms, go to next step.
5. Check ground circuit for open
   
   Turn ignition switch to OFF position. Disconnect RCM connector. Measure resistance between chassis ground and RCM connector terminal No. 21 (Black/Orange wire, circuit No. 649). See Figure. If resistance is more than 100 ohms, repair open in Black/Orange wire. See WIRING DIAGRAMS . Go to step  7. If resistance is less than 100 ohms, replace RCM. Go to next step.
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, fault is hard. Go to step  2. If DTC B1921 was not retrieved, fault is intermittent. Check for cause of intermittent high resistance in Black/Orange 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. Reactivate air bag system. See ACTIVATING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Clear all DTCs. See CLEARING FAULT CODES  under DIAGNOSTICS.