Possible Causes

A short to battery in left seat belt pretensioner circuit could be caused damaged wiring, connectors or terminals or RCM internal fault.

1. Check for hard or intermittent DTCs
   
   Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Retrieve and record any continuous DTCs. See RETRIEVING FAULT CODES  . Clear continuous DTCs. See CLEARING FAULT CODES  under DIAGNOSTICS. Perform on-demand self-test. See ON-DEMAND SELF-TEST  under DIAGNOSTICS. If DTC B1878 was retrieved during on-demand self-test, fault is hard. Go to next step. If DTC B1878 was not retrieved, fault is intermittent. Go to step  4 .
2. Check left seat belt pretensioner
   
   Turn ignition switch to OFF position. Access and disconnect RCM harness connector. See RESTRAINTS CONTROL MODULE (RCM)  under REMOVAL & INSTALLATION. Disconnect left seat belt pretensioner harness connector C323. Turn ignition to ON position. Measure voltage between ground and RCM harness connector C2041, terminals No. 18 (Light Green/Red wire, circuit No. 1079) and No. 22 (Light Green/Black wire, circuit No. 1080). See Figure . If voltage is more than 0.2 volt at either terminal, repair short to battery in Light Green/Red or Light Green/Black wires. See WIRING DIAGRAMS  . Go to step  5 . If voltage is less than 0.2 volt at both terminals, go to next step.
   NOTE: Ensure all air bag system simulators, sensor electrical connectors and RCM electrical connectors are connected prior to carrying out on-demand self-test, or erroneous faults may be set.
3. Confirm RCM fault
   
   Turn ignition switch to OFF position. Reconnect left seat belt pretensioner harness connector C323. Reconnect RCM harness connector. Turn ignition switch to ON position. Perform on-demand self-test. If DTC B1878 was retrieved during on-demand self-test, replace RCM. Go to step  5 . If DTC B1878 was not retrieved during on-demand self-test, fault is corrected. Go to step  5 .
4. Check for intermittent fault
   
   Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Turn ignition switch to ON position. Perform on-demand self-test. If DTC B1878 was retrieved during on-demand self-test, check for intermittent fault in Light Green/Red or Light Green/Black wire. Repair any intermittent problems found. If intermittent problems are found and repaired, go to next step. If intermittent problems are not found, go to step  2 . If DTC B1878 was not retrieved, check for cause of intermittent fault. Attempt to recreate fault by flexing wire harness and cycling ignition switch frequently. Activate systems in same wire harness. See WIRING DIAGRAMS  . Repair any intermittent problems found. Go to next step.
5. 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 DTCs were retrieved, reconnect air bag system. Activate air bag system. See ACTIVATING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Perform system operation check. See SYSTEM OPERATION CHECK  . Clear all DTCs. See CLEARING FAULT CODES  under DIAGNOSTICS.