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Test 7: No Module/Network Communications - ISO 9141 Link

WARNING: This page is about a different car, the 2000 Mazda B4000, 2000 Mazda B3000, and 2000 Mazda B2500. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: ISO 9141 communication network will not function if Light Blue/White wire is shorted to ground or power. Steps  3- 9 are used for locating a short.
  1. Turn ignition switch to OFF position. Inspect Data Link Connector (DLC) for physical damage, bent terminals or corrosion. Pay particular attention to terminal No. 7 (Light Blue/White wire). See Figure. Repair connector as necessary and retest system for normal operation. If connector is okay, go to next step.
  2. Ensure ignition switch is in OFF position. Disconnect GEM 26-pin harness connector (T-221). Measure resistance of Light Blue/White wire between terminal No. 25 at GEM harness connector and terminal No. 7 at DLC. See Figure and Figure . If resistance is greater than 5 ohms, repair open in Light Blue/White wire between DLC and GEM connector. Retest system for normal operation. If resistance is 5 ohms or less, connect GEM harness connector and proceed as follows:
    • If vehicle is equipped with a Remote Anti-Theft Personality (RAP) module and/or a 4-Wheel Anti-Lock Brake System (4WABS) module, go to next step.
    • If vehicle is equipped with a 4WABS module only, go to step  4.
    • If vehicle is not equipped with a RAP module or a 4WABS module, go to step  5.
  3. Disconnect 84-pin in-line harness connector (X-201), located behind left corner of instrument panel. Turn ignition switch to ON position. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 16 (Orange wire) at DLC. See Figure. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 4 (Black wire) at DLC. If either reading indicates zero volts, go to next step (vehicles with 4WABS) or step  5 (vehicles without 4WABS). If both readings indicate voltage, go to step  7.
  4. Turn ignition switch to OFF position. Disconnect 40-pin bulkhead harness connector (X-134), located at left rear of engine compartment. Turn ignition switch to ON position. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 16 (Orange wire) at DLC. See Figure. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 4 (Black wire) at DLC. If either reading indicates zero volts, go to next step. If both readings indicate voltage, go to step  8.
  5. Turn ignition switch to OFF position. Disconnect GEM 26-pin harness connector (T-221). Turn ignition switch to ON position. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 16 (Orange wire) at DLC. See Figure and Figure . Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 4 (Black wire) at DLC. If either reading indicates zero volts, go to next step. If both readings indicate voltage, replace GEM and retest system for normal operation.
  6. Turn ignition switch to OFF position. Deactivate air bag system. See AIR BAG RESTRAINT SYSTEMS - PICKUP article. Disconnect air bag diagnostic monitor harness connector. Turn ignition switch to ON position. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 16 (Orange wire) at DLC. See Figure and Figure .

    Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 4 (Black wire) at DLC. If either reading indicates zero volts, repair Light Blue/White wire between DLC, air bag diagnostic monitor connector, GEM connector, 84-pin in-line connector (X-201), and/or 40-pin bulkhead connector (X-134). Retest system for normal operation. If both readings indicate voltage, replace air bag diagnostic monitor and retest system for normal operation.

  7. Turn ignition switch to OFF position. Disconnect 84-pin in-line harness connector (X-201). Disconnect RAP module 26-pin harness connector (T-410). Turn ignition switch to ON position. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 16 (Orange wire) at DLC. See Figure. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 4 (Black wire) at DLC. If either reading indicates zero volts, repair Light Blue/White wire between 84-pin in-line harness connector (X-201) and RAP module 26-pin harness connector. If both readings indicate voltage, replace RAP module and retest system for normal operation.
  8. Turn ignition switch to OFF position. Disconnect 40-pin bulkhead harness connector (X-134). Disconnect 4WABS module 25-pin harness connector. Turn ignition switch to ON position. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 16 (Orange wire) at DLC. See Figure. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 4 (Black wire) at DLC. If either reading indicates zero volts, go to next step. If both readings indicate voltage, replace 4WABS module. Retest system for normal operation.
  9. Turn ignition switch to OFF position. Disconnect 12-pin bulkhead harness connector (X-179). Turn ignition switch to ON position. Measure voltage between terminals No. 7 (Light Blue/White wire) and No. 16 (Orange wire) at DLC. See Figure. Measure voltage between terminal No. 7 (Light Blue/White wire) and terminal No. 4 (Black wire) at DLC.

    If either reading indicates zero volts, repair Light Blue/White wire between 40-pin bulkhead harness connector (X-134) and 12-pin bulkhead harness connector (X-179). Retest system for normal operation. If both readings indicate voltage, repair Light Blue/White wire between 12-pin bulkhead harness connector (X-179) and 4WABS module. Retest system for normal operation.

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