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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 A: Air Bag Warning Light On Continuously-RCM Disconnected, Inoperative Or Lost-Low Ignition Feed >> Possible Causes

Possible Causes

An AIR BAG warning light that is continuously illuminated may be caused by worn or damaged camming beam, ignition circuit damage, disconnected Restraints Control Module (RCM) module, loss of RCM ground circuits, inoperative RCM or damaged air bag system wiring harness.

  1. Check for continuous or on-demand self-test DTC

    Ensure ignition is off. Connect scan tool to Data Link Connector (DLC). See USING SCAN TOOL  . Turn ignition switch to RUN position. Retrieve and record any continuous Diagnostic Trouble Codes (DTCs). See RETRIEVING DIAGNOSTIC TROUBLE CODES (DTCS)  under DIAGNOSTICS. Clear continuous DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS)  under DIAGNOSTICS. Perform on-demand self-test. See ON-DEMAND SELF-TEST  under DIAGNOSTICS. If continuous DTCs were retrieved, go to step  3 . If on-demand 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, go to next step.
  2. Check RCM connection

    Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Access RCM. See RESTRAINTS CONTROL MODULE (RCM)  under REMOVAL & INSTALLATION. Ensure RCM connector is fully connected and Red locking tab is engaged. If RCM connector is fully connected and Red locking tab is engaged, go to next step. If RCM connector is not fully connected and-or Red locking tab is not engaged, reconnect connector and engage locking tab. Go to step  7 .
    NOTE: Shorting bars may be accessed by prying out Blue cover from harness side of connector.
  3. Check RCM connector

    Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Access RCM and disconnect connector. See RESTRAINTS CONTROL MODULE (RCM)  under REMOVAL & INSTALLATION. Inspect RCM, component side of connector, for worn or damaged camming beam and-or any foreign material. See Fig 1 . Inspect RCM connector for worn, damaged or dislodged shorting bar at terminals No. 20 and 21. See Fig 1 . If camming beams and shorting bars are okay, go to next step. If camming beams and shorting bars are defective, repair or replace as necessary and go to step  7 .
  4. Check RCM ignition circuit connection

    Turn ignition switch to RUN position. Measure voltage between ground and RCM harness connector terminal No. 2 (White-Orange wire). See Fig 2 . If voltage is 9-16 volts, go to next step. If voltage is not 9-16 volts, repair open in White-Orange wire. See WIRING DIAGRAMS  . Go to step  7 .
  5. Check ground circuit for open

    Turn ignition switch to OFF position. Measure resistance between sheet metal ground near RCM and RCM harness connector terminal No. 21 (Black-White wire). If resistance is less than 10 ohms, go to next step. If resistance is more then 10 ohms, repair open in Black-White wire (circuit No. 397) and go to step  7 .
  6. Check for short to ground

    Reconnect RCM connector. Access and disconnect instrument cluster connector C276. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. Measure resistance between ground and instrument cluster connector C276, terminal No. 12 (Black-Yellow wire). See Fig 3 . If resistance is less than 10 megohms, repair short to ground in Black-Yellow wire (circuit No. 608) and go to next step. If resistance is more than 10 megohms, replace RCM and 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 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 and 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.
    Fig 1: Identifying Camming Beams & Shorting Bars
    G99C00096Courtesy of FORD MOTOR CO.
    Fig 2: Identifying Restraints Control Module Connector C276
    G99I00156Courtesy of FORD MOTOR CO.
    Fig 3: Identifying Instrument Cluster Connector C250
    G99J00157Courtesy of FORD MOTOR CO.