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DTC B1921 - Diagnostic Monitor Not Mounted To Vehicle Properly

WARNING: This page is about a different car, the 1996 Ford Ranger and 1996 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Before proceeding, see SERVICE PRECAUTIONS . After servicing has been performed, recheck AIR BAG warning light. If system is okay, install air bag modules and reactivate air bag system.

  1. Verify Condition

    Connect NGS tester to DLC. Perform ON-DEMAND SELF-TEST. If DTC B1921 is retrieved, go to step 2). If DTC B1921 is not retrieved, go to step 5).

  2. Measure Resistance

    Connect NGS to DLC. Select IABM. Select PID/Data Monitor and Record. Select PID BRACKET. If resistance is more than 3 ohms, deactivate system, Remove air bag diagnostic monitor and bracket. See COMPLETE SYSTEM DEACTIVATION . Thoroughly clean mounting surfaces. Reinstall air bag diagnostic monitor and go to next step. If resistance is less than 3 ohms, go to step 4).

  3. Recheck Resistance

    Again, measure resistance between ground and diagnostic monitor bracket. If resistance is less than 3 ohms, cleaning diagnostic monitor mounting surfaces in step 2) has corrected problem. Go to step 8). If resistance is more than 3 ohms, go next step

  4. Check Reference Ground

    Check attachment of ground connections and splices in circuit 570 (Black/White wire) feeding diagnostic monitor harness terminals C1-10 and C1-18. See Figure. If poor connections are noted repair circuit as necessary. Add a ground strap from circuit 570 (Black/White wire) to one of the air bag diagnostic monitor mounting fasteners. Connect air bag diagnostic monitor and go to step 8). If no poor connections are noted, replace air bag diagnostic monitor. Reconnect system. Verify system. Reactivate system and go to step 8)

  5. Check For DTC Service

    Deactivate system. See COMPLETE SYSTEM DEACTIVATION . If DTC B1921 has just been repaired, go to step 8). If DTC B1921 has not just been repaired, go to next step.

  6. Check For Corrosion

    Inspect diagnostic monitor bracket and mounting surfaces. Look for signs of corrosion or poor contact. If significant corrosion is found, replace air bag diagnostic monitor. Verify system. Reactivate system and go to step 8).

  7. Check Circuit 570 (Black/White wire)

    Check attachment of ground connections and splices in circuit 570 (Black/White wire) feeding diagnostic monitor harness connector terminals C1-10 and C1-18. See Figure. If poor connections are noted, repair as necessary. See step 4). Add ground strap from circuit 570 (Black/White wire) to one of diagnostic monitor mounting fasteners. Connect diagnostic monitor and go to step 8). If no poor connections are noted, remove air bag diagnostic monitor and bracket from vehicle and thoroughly clean mounting surfaces. Replace air bag diagnostic monitor. Re-examine fault code and look for causes of high resistance in diagnostic monitor bracket ground. Repair any intermittent faults and go to step 8).

  8. Check For Other DTCs

    Connect NGS to DLC. If other DTCs are retrieved go to proper DTC test. If no other DTCs are retrieved, reactivate system and clear all DTCs.
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