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

NOTE: Depending on module configuration, with all modules connected and with ignition switch in RUN position or with engine running, 2-3 volts should be present at Data Link Connector (DLC) terminal No. 7 (Light Blue/White wire). This is the International Standards Organization (ISO) 9141 diagnostic bus communications network circuit.
NOTE: After making any repair, perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM.
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 an ohmmeter to isolate wiring harness shorts or opens.
  1. Turn ignition switch to LOCK position. Inspect Worldwide Diagnostic System (WDS) tester or New Generation Star (NGS) tester connector for loose, damaged or corroded terminals. If connector is okay, go to next step. If connector is faulty, repair or replace connector as necessary.
  2. Inspect Data Link Connector (DLC) for physical damage, bent terminals or corrosion. DLC is located under instrument panel between steering column and radio. See Figure. If connector is okay, go to next step. If connector is faulty, repair or replace as necessary. After repair, test system for normal operation.
  3. Disconnect Generic Electronic Module (GEM) 20-pin harness connector C201b, located attached to under side of Central Junction Box (CJB). See Figure. Inspect GEM 20-pin harness connector C201b for damage, bent terminals or corrosion. If problem exists, repair as necessary. Measure resistance between DLC terminal No. 7 and GEM harness connector C201b terminal No. 3 (Light Blue/White wire). See Figure and Figure . SeeWIRING 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 GEM and DLC.
  4. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire), and No. 7 (Light Blue/White wire) and No. 16 (Light Green/Red wire). See Figure. SeeWIRING DIAGRAMS . If voltage is not present at all measurements and vehicle is equipped with ABS, go to next step. If voltage is not present at all measurements and vehicle is not equipped with Anti-Lock Brake System (ABS), go to step  7. If voltage is present at any measurement, replace GEM. See GENERIC ELECTRONIC MODULE  under REMOVAL & INSTALLATION. After repair, test system for normal operation.
  5. Turn ignition switch to LOCK position. Disconnect ABS/TC module 30-pin harness connector C135, located in left front of engine compartment. See Figure. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire), and No. 7 (Light Blue/White wire) and No. 16 (Light Green/Red wire). SeeWIRING DIAGRAMS . If voltage is not present at all measurements, go to next step. If voltage is present at any measurement, replace ABS/TC module. See ANTI-LOCK BRAKE CONTROL MODULE  under REMOVAL & INSTALLATION. After repair, test system for normal operation.
  6. Turn ignition switch to LOCK position. Disconnect 42-pin in-line harness connector C264, located behind left side of instrument cluster. See Figure. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire), and No. 7 (Light Blue/White wire) and No. 16 (Light Green/Red wire). SeeWIRING DIAGRAMS . If voltage is not present at all measurements, go to next step. If voltage is present at any measurement, repair short in appropriate circuit between in-line harness connector C264 and ABS module. After repair, test system for normal operation.
  7. Turn ignition switch to LOCK position. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS. Disconnect Restraint Control Module (RCM) 24-pin harness connector C310a, located behind center of instrument panel, on tunnel. See Figure. Reconnect GEM harness connector C201b. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire), and No. 7 (Light Blue/White wire) and No. 16 (Light Green/Red wire). SeeWIRING DIAGRAMS . If voltage is not present at all measurements, go to next step. If voltage is present at any measurement, replace RCM. See RESTRAINT CONTROL MODULE  under REMOVAL & INSTALLATION. After repair, test system for normal operation.
  8. Turn ignition switch to LOCK position. Disconnect 38-pin in-line harness connector C263, located behind right side of instrument cluster. See Figure. Turn ignition switch to RUN position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 7 (Light Blue/White wire), and No. 7 (Light Blue/White wire) and No. 16 (Light Green/Red wire). SeeWIRING DIAGRAMS . If voltage is not present at all measurements, repair short in appropriate circuit between in-line harness connector C264 and GEM. If voltage is present at any measurement, repair short in appropriate circuit between in-line harness connector C263 and RCM. After repair, test system for normal operation.
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