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Home >> Ford >> 2000 >> Contour SE, 2.5 L, Standard >> Repair and Diagnosis >> Restraints >> Air Bag, SRS >> Air Bag Restraint Systems >> Diagnostic Tests >> Test D: RCM Bracket Ground Resistance High (DTC B1921) >> Possible Causes

Possible Causes

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

  1. Check for hard or intermittent DTC

    Ensure ignition is off. Connect NGS tester to DLC. See USING NGS TESTER  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 off. Access RCM. See RESTRAINTS CONTROL MODULE  under REMOVAL & INSTALLATION. Inspect RCM, mounting bracket and mounting surface for damage or corrosion. Inspect RCM bracket 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/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, reattach 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 and go to step  7 . If resistance is less than 100 ohms, go to next step.

  5. Check ground circuit for open

    Turn ignition off. Disconnect RCM connector. Measure resistance between chassis ground and RCM connector terminal No. 21 (Black/Red wire). See Figure . If resistance is more than 100 ohms, repair open in Black/Red wire and go to step  7 . See WIRING DIAGRAMS  . If resistance is less than 100 ohms, replace RCM. Go to next step.

  6. Check for intermittent fault

    Refer to continuous DTCs recorded in step  1 . If DTC retrieved in step 1was an intermittent fault, check for cause of high resistance in Black/Red wire (circuit 649). 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 an intermittent fault, 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. 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.
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