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Test G: No Module/Network Communication - ISO 9141 Network

NOTE: Depending on module configuration, with all modules connected and with ignition on, 2-3 volts may be present at Data Link Connector (DLC) terminal No. 7 (Light Blue/White wire). This is the International Standards Organization (ISO) 9141 diagnostic communications network circuit.
  1. Turn ignition off. Inspect Data Link Connector (DLC) for physical damage, bent terminals or corrosion. Pay particular attention to terminal No. 7 (Light Blue/White wire). Repair connector as necessary and retest system for normal operation. If connector is okay, go to next step.
  2. Ensure ignition is off. Disconnect GEM/CTM 26-pin connector C221, located behind center of instrument panel. Measure resistance of Light Blue/White wire between GEM connector C221 terminal No. 25 and DLC terminal No. 7. See Figure and Figure . If resistance is 5 ohms or more, repair open in Light Blue/White wire between GEM and DLC. If resistance is less than 5 ohms and vehicle is equipped with 4WABS module, reconnect GEM connector C221, then go to next step. If resistance is less than 5 ohms and vehicle is not equipped with 4WABS module, reconnect GEM connector C221, then go to step  4.
  3. Turn ignition off. Disconnect 40-pin bulkhead connector C136 located at left rear of engine compartment. See Figure, Figure or Figure . Turn ignition on. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Orange wire). See Figure. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 4 (Black wire). If either reading indicates no voltage, go to next step. If both readings indicate voltage, go to step  7.
  4. Turn ignition off. Disconnect GEM/CTM 26-pin connector C221, located behind center of instrument panel. Turn ignition on. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Orange wire). See Figure and Figure . Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 4 (Black wire). If either reading indicates no voltage, go to next step. If both readings indicate voltage, replace GEM/CTM and retest system for normal operation.
  5. Turn ignition off. Deactivate air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM in AIR BAG RESTRAINT SYSTEMS - RANGER article. Disconnect Restraint Control Module (RCM) 26-pin connector. Reconnect GEM/CTM connector C221. Turn ignition on. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Orange wire). See Figure. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 4 (Black wire). If either reading indicates no voltage, go to next step. If both readings indicate voltage, replace RCM and retest system for normal operation.
  6. Turn ignition off. Disconnect RAP module 26-pin connector C410, located at left rear corner of cab. Turn ignition on. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Orange wire). See Figure. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 4 (Black wire). If any reading indicates no voltage, repair Light Blue/White wire between DLC and RCM, GEM/CTM, RAP module or female half of bulkhead connector C136. Retest system for normal operation. If both readings indicate voltage, replace RAP module and retest system for normal operation.
  7. Turn ignition off. Reconnect bulkhead connector C136. Disconnect 25-pin 4WABS module connector located at left side of engine compartment. See Figure, Figure or Figure . Turn ignition on. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Orange wire). See Figure. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 4 (Black wire). If either reading indicates no voltage, go to next step. If both readings indicate voltage, replace 4WABS module and retest system for normal operation.
  8. Turn ignition off. Disconnect 12-pin in-line connector C179, located at left side of engine compartment. See Figure, Figure or Figure . Turn ignition on. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Orange wire). See Figure. Measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 4 (Black wire). If either reading indicates no voltage, repair Light Blue/White wire between male half of bulkhead connector C136 and female half of in-line connector C179. Retest system for normal operation. If both readings indicate voltage, repair Light Blue/White wire between male half of in-line connector C179 and 4WABS module. Retest system for normal operation.
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