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Home >> Ford >> 1998 >> Mustang Base, 2D Convertible, Automatic >> Repair and Diagnosis >> Restraints >> Air Bag, SRS >> Supplemental Inflatable Restraint System >> Diagnostic Tests >> Test B - Module Communication Error >> Possible Causes

Possible Causes

Module communication error might be caused by faulty NGS tester, data link connector (DLC), diagnostic monitor, or related circuitry.

  1. Check For Ignition Voltage  - Disable system. See DISABLING & ACTIVATING AIR BAG SYSTEM  . Disconnect diagnostic monitor. Diagnostic monitor is Blue box located below climate control assembly. Turn ignition switch to RUN position. Measure voltage between ground and diagnostic monitor connector C276, terminal No. 6 (Purple/Orange wire). See Figure . If battery voltage is present, go to next step. If battery voltage is not present, repair open in Purple/Orange wire. Go to step 6).
  2. Check Circuit 57 For Open  - Measure resistance between ground and diagnostic monitor connector C276, terminal No. 18 (Black wire). If resistance is less than 3 ohms, go to next step. If resistance is more than 3 ohms, repair open in Black wire. Go to step 6).
  3. Check For Battery Voltage  - Measure voltage between ground and diagnostic monitor connector C276, terminal No. 14 (Red/White wire). If battery voltage is present, go to step 6). If battery voltage is not present, go to next step.
  4. Check Battery Fuses  - Disable system. See DISABLING & ACTIVATING AIR BAG SYSTEM  . Check fuse No. 4 (10-amp), located in instrument panel fuse block left of steering column. If fuse is blown, go to next step. If fuse is okay, repair open in Red/White wire between fuse and diagnostic monitor connector. See WIRING DIAGRAMS  . Go to step 6).
    WARNING: Certain fault conditions (DTC B1913 or B1914) may cause air bag diagnostic monitor to intentionally open fuse No. 4 (10-amp) to disarm air bag system. DO NOT  substitute another fuse value for 10-amp fuse. Any other fuse value may cause future disarming failure and danger to occupants of vehicle. Once diagnostic monitor has disarmed SRS, it will not attempt to do so again until appropriate fault code (DTC B1913 or B1914) has been cleared. DO NOT  reactivate system until all fault codes have been serviced and repaired.
  5. Check For Short In Harness  - Replace fuse No. 4 (10-amp). If fuse is okay, go to next step. If fuse blows again, repair short to ground in Red/White wire). See WIRING DIAGRAMS  . Go to next step.
  6. Check Module Communication  - Reconnect system components. Turn ignition switch to RUN position. If diagnostic monitor communicates with NGS tester, reactivate system. See DISABLING & ACTIVATING AIR BAG SYSTEM  . Check AIR BAG warning light for proper system function. See SYSTEM OPERATION CHECK  . If diagnostic monitor does not communicate with NGS tester, go to next step.
  7. Check diagnostic monitor Connector C277  - Turn ignition switch to OFF position. Disable system. See DISABLING & ACTIVATING AIR BAG SYSTEM  . Disconnect diagnostic monitor connector C277. See Figure . Inspect diagnostic monitor connector C277, terminal No. 12 (Light Blue/White wire) for good connection. If pin and connection is okay, go to next step. If pin and/or connection is damaged, repair as necessary and return to step 6).
  8. Check ISO 914 Network For Open  - Measure resistance of Light Blue/White wire between diagnostic monitor connector C277, terminal No. 12 and Data Link Connector (DLC). DLC is located under left side of instrument panel, to right of steering column. If resistance is less than 5 ohms, replace diagnostic monitor and return to step 6). See DIAGNOSTIC MONITOR  under REMOVAL & INSTALLATION. If resistance is more than 5 ohms, repair open in Light Blue/White wire and return to step 6).
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