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Home >> Ford >> 2001 >> Mustang Base, 2D Convertible, Automatic >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Supplemental Inflatable Restraint System >> Diagnostic Tests >> Test Q: Air Bag Warning Light Circuit Short To Battery (DTC B1870) >> Possible Causes

Possible Causes

AIR BAG warning light inoperative condition could be caused by damaged Black-Yellow wire (circuit 608) or an instrument cluster malfunction.

  1. Check for hard or intermittent DTC

    Ensure ignition is off. 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 B1870 was retrieved during on-demand self-test, fault is hard. Go to next step. If DTC B1870 was not retrieved, fault is intermittent. Go to step  5 .

  2. Check RCM

    Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Access RCM and disconnect harness connector. See RESTRAINTS CONTROL MODULE (RCM)  under REMOVAL & INSTALLATION. Turn ignition switch to RUN position. If AIR BAG warning light illuminates, replace RCM. Go to step  5 . If AIR BAG warning light does not illuminate, go to next step.

  3. Check air bag warning light circuit

    Turn ignition switch to OFF position. Disconnect negative battery cable. Access and disconnect instrument cluster connector C250. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. Turn ignition switch to RUN position. Measure resistance between RCM connector terminals No. 2 (White-Orange wire) and No. 20 (Black-Yellow wire). See Figure . If resistance is less than 10 megohms, repair short to battery in Black-Yellow wire (circuit No. 608). See WIRING DIAGRAMS  . Go to step  5 . If resistance is more than 10 megohms, diagnose and repair instrument cluster malfunction as necessary. Go to step  5 .

  4. Check for intermittent fault

    Refer to continuous DTCs recorded in step  1 . If DTC retrieved in step  1 was a intermittent fault, check for cause of intermittent short to battery on Black-Yellow wire (circuit No. 608). 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. If DTC retrieved in step  1 was not a intermittent fault, 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 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. Prove out system. See PROVE OUT SYSTEM  under DIAGNOSTICS. Clear all DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS)  under DIAGNOSTICS.
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