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Home >> Ford >> 2001 >> Focus ZTS, Standard >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Supplemental Inflatable Restraint System >> Diagnostic Tests >> Test T: Left Seat Belt PRETENSIONER Circuit Open (DTC B1877) >> Possible Causes

Possible Causes

A left seat belt pretensioner circuit high resistance could be caused by high resistance on Green-Blue wire (circuit 15S-JA33), high resistance on Black-Blue wire (circuit 91S-JA33), high resistance in left seat belt pretensioner or an internal RCM fault.

  1. Check left seat belt pretensioner

    Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Turn ignition switch to RUN position. Perform on-demand self-test. See ON-DEMAND SELF-TEST  under DIAGNOSTICS. If DTC B1877 is retrieved, go to next step. If DTC B1877 is not retrieved, replace left seat belt pretensioner. See SEAT BELT PRETENSIONER  under REMOVAL & INSTALLATION. Activate air bag system. See ACTIVATING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Clear DTCs. See CLEARING FAULT CODES  under DIAGNOSTICS. Repeat on-demand self-test.

  2. Check left seat belt pretensioner circuits

    Turn ignition switch to OFF position. Access RCM and disconnect harness connector C423. See RESTRAINTS CONTROL MODULE (RCM)  under REMOVAL & INSTALLATION. Disconnect left seat belt pretensioner simulator. Measure resistance of Green-Blue wire between RCM harness connector C423, terminal No. 11 and left under-seat connector C30, terminal No. 5. See Figure & Figure . Resistance should be less than 5 ohms. Measure resistance between ground and RCM harness connector C423, terminal No. 11 (Green-Blue wire). Resistance should be more than 10 k-ohms. If resistances are as specified, go to next step. If resistances are not as specified, repair Green-Blue wire as necessary. See WIRING DIAGRAMS . Activate air bag system. Clear DTCs. Repeat on-demand self-test.

  3. Check left seat belt pretensioner circuits

    Measure resistance of Black-Blue wire between RCM harness connector C423, terminal No. 12 and left under-seat connector C30, terminal No. 6. If resistance is less than 5 ohms replace RCM. Activate air bag system. Clear DTCs. Repeat on-demand self-test. If resistance is more than 5 ohms, repair open in Black-Blue wire. Activate air bag system. Clear DTCs. Repeat on-demand self-test.
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