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

WARNING: This page is about a different car, the 2002 Mercury Grand Marquis and 2002 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Depending on module configuration, with all modules connected and ignition switch in RUN position or engine running, 2-3 volts may exist at Data Link Connector (DLC) terminal No. 7 (Light Blue/White wire). This is the International Standards Organization (ISO) 9141 diagnostic communications network circuit.
NOTE: Perform all voltage and resistance tests using a Digital Volt-Ohm Meter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.
  1. Turn ignition switch to LOCK position. Inspect DLC terminal No. 7 (Light Blue/White wire) for physical damage, bent terminals or corrosion. DLC is located under instrument panel between steering column and radio. See Figure. If DLC connector and terminals are okay, go to next step. If connector and terminals are faulty, repair or replace as necessary. After repair, test system for normal operation.
  2. Disconnect Lighting Control Module (LCM) harness connector C2145c. See Figure. LCM connector C2145c is located behind left side of dash panel. See Figure. Inspect harness connector for loose, damaged or corroded terminals. If connector and terminals are okay, go to next step. If connector and terminals are faulty, repair or replace as necessary. After repair, test system for normal operation.
  3. Measure resistance between LCM harness connector C2145c terminal No. 8 and DLC terminal No. 7 (Light Blue/White wire). See Figure and Figure . See WIRING DIAGRAMS . If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open circuit in Light Blue/White wire between LCM and DLC. After repair, test system for normal operation.
  4. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire). See Figure. See WIRING DIAGRAMS . Also, measure voltage between DLCterminals No. 7 (Light Blue/White wire) and No. 16 (Yellow/Black wire). If both readings indicate voltage, replace LCM. See LIGHTING CONTROL MODULE  under REMOVAL & INSTALLATION. If either measurement indicates zero voltage, on vehicles equipped with Driver's Door Module (DDM), go to next step. On vehicles without DDM, go to step  8. After repair, test system for normal operation.
  5. Turn ignition switch to LOCK position. Disconnect Driver's Door Module (DDM) harness connector C501a. See Figure. DDM connector C501a is located behind driver's door trim panel. See Figure. Inspect harness connector for loose, damaged or corroded terminals. If connector and terminals are okay, go to next step. If connector and terminals are faulty, repair or replace as necessary. After repair, test system for normal operation.
  6. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire). See Figure. See WIRING DIAGRAMS . Also, measure voltage between terminals No. 7 (Light Blue/White wire) and No. 16 (Yellow/Black wire). If either measurement indicates zero voltage, go to next step. If both readings indicate voltage, replace DDM. See DRIVER'S DOOR MODULE  under REMOVAL & INSTALLATION. After repair, test system for normal operation.
  7. Turn ignition switch to LOCK position. Disconnect 16-pin in-line harness connector C213. See Figure. In-line harness connector C213 is located behind left side rocker panel. See Figure. Turn ignition switch to RUN position. Measure voltage between terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire). See Figure. See WIRING DIAGRAMS . Also, measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Yellow/Black wire). If either measurement indicates zero volts, go to next step. If both readings indicate voltage, repair short circuit to voltage or ground in Light Blue/White wire between female half of in-line harness connector C213 and DDM. After repair, test system for normal operation.
  8. Turn ignition switch to LOCK position. Deactivate air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS. Connect LCM harness connector C2145c. Disconnect Restraint Control Module (RCM) 11-pin harness connector C310b. See Figure. RCM harness connector C310b is located behind center of dash panel. See Figure. Inspect harness connector for loose, damaged or corroded terminals. If connector and terminals are okay, go to next step. If connector and terminals are faulty, repair or replace as necessary. After repair, test system for normal operation.
  9. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire). See Figure. See WIRING DIAGRAMS . Also, measure voltage between DLC terminals No. 7 (Light Blue/White wire) and No. 16 (Yellow/Black wire). If both measurements indicate voltage, replace RCM. See RESTRAINT CONTROL MODULE  under REMOVAL & INSTALLATION. If either measurement indicates zero voltage, repair open or short circuit to ground in Light Blue/White wire between DLC, female half of in-line harness connector C213, RCM and DDM. After repair, clear DTCs and test system for normal operation.
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