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

WARNING: This page is about a different car, the 2002 Ford Pickup. 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 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 communications network circuit.
  1. Turn ignition switch to LOCK position. Inspect Data Link Connector (DLC) for harness connector for loose, damaged or corroded terminals. DLC is located below driver's side instrument cluster, right of steering wheel. If harness connector is okay, go to next step. If harness connector is damaged, repair as necessary.
  2. Disconnect Generic Electronic Module (GEM) 26-pin harness connector C201a. GEM is located below driver's side of instrument panel, left of steering column. See Figure. Measure resistance in Light Blue/White wire between GEM harness connector C201a terminal No. 25 and DLC terminal No. 7. See Figure and Figure . If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in Light Blue/White wire between GEM harness connector C201a and DLC. See WIRING DIAGRAMS .
  3. Ensure GEM harness connector C201a is disconnected. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST . If NGS tester does not indicate system PASSED, go to next step. If NGS tester indicates system PASSED, go to step  14.
  4. Turn ignition switch to LOCK position. Connect GEM harness connector C201a. Disconnect Central Security Module (CSM) harness connector C274a. Measure resistance in Light Blue/White wire between CSM harness connector terminal No. 3 and DLC terminal No. 7. If resistance is more than 5 ohms, go to next step. If resistance is 5 ohms or less, go to step  7.
  5. Disconnect Gray in-line harness connector C248. Harness connector C248 is located behind left side of instrument panel. Inspect harness connector for loose, damaged or corroded terminals. If harness connector is okay, go to next step. If harness connector is damaged, repair as necessary.
  6. Measure resistance in Light Blue/White wire between Gray in-line harness connector C248 (female side) terminal No. 16 and DLC terminal No. 7. If resistance is more than 5 ohms, repair open or short in Light Blue/White wire between Gray in-line harness connector C248 (female side) and DLC. If resistance is 5 ohms or less, repair open or short in Light Blue/White wire between Gray in-line harness connector C248 (male side) and DLC.
  7. Ensure CSM harness connector C274a is disconnected. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST . If NGS tester does not indicate system PASSED, go to next step. If NGS tester indicates system PASSED, go to step  15.
  8. Turn ignition switch to LOCK position. Connect CSM harness connector C274a. Deactivate air bag system. See DISABLING SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS. Disconnect Restraint Control Module (RCM) harness connector C2041. Measure resistance in Light Blue/White wire between RCM harness connector C2041 terminal No 5 and DLC terminal No 7. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in Light Blue/White wire between RCM and DLC. See WIRING DIAGRAMS .
  9. Ensure RCM harness connector C2041 is disconnected. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST . If NGS tester does not indicate system PASSED, go to next step. If NGS tester indicates system PASSED, go to step  16
  10. Turn ignition switch to LOCK position. Connect RCM harness connector C2041. Disconnect 4-Wheel Anti-Lock Brake System (4WABS) control module harness connector C155. Measure resistance in Light Blue/White wire between 4WABS control module harness connector C155 terminal No. 1 and DLC terminal No 7. If resistance is more than 5 ohms, go to next step. If resistance is 5 ohms or less, go to step  13.
  11. Disconnect Gray in-line harness connector C140. Harness connector C140 is located in left rear of engine compartment. Inspect harness connector for loose, damaged or corroded terminals. If harness connector is okay, go to next step. If harness connector is damaged, repair as necessary.
  12. Measure resistance in Light Blue/White wire between Gray in-line harness connector C140 (male side) terminal No. 29 and DLC terminal No. 7. If resistance is more than 5 ohms, repair open or short in Light Blue/White wire between Gray in-line harness connector C140 (female side) and DLC. If resistance is 5 ohms or less, repair open or short in Light Blue/White wire between Gray in-line harness connector C140 (male side) and DLC.
  13. Ensure 4WABS control module C155 is disconnected. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST . If NGS tester does not indicate system PASSED, go to next step. If NGS tester indicates system PASSED, go to step  17
  14. Disconnect all GEM harness connectors. Check GEM harness connectors for loose, pushed out or corroded terminals. Connect all disconnected connectors and retest system. If problem still exists, replace GEM and perform data link test. See GENERIC ELECTRONIC MODULE  in REMOVAL & INSTALLATION. See DATA LINK DIAGNOSTIC TEST . If problem does not exist, system is operating normally. Clear all diagnostic trouble codes and perform self test.
  15. Disconnect all CSM harness connectors. Check CSM harness connectors for loose, pushed out or corroded terminals. Connect all disconnected CSM harness connectors and retest system. If problem still exists, replace CSM and perform data link test. See CENTRAL SECURITY MODULE  in REMOVAL & INSTALLATION. See DATA LINK DIAGNOSTIC TEST . If problem does not exist, system is operating normally. Clear all diagnostic trouble codes and perform self test.
  16. Disconnect all RCM harness connectors. Check RCM harness connectors for loose, pushed out or corroded terminals. Connect all disconnected connectors and retest system. If problem still exists, replace RCM and perform data link test. See RESTRAINT CONTROL MODULE  in REMOVAL & INSTALLATION. See DATA LINK DIAGNOSTIC TEST . If problem does not exist, system is operating normally. Clear all diagnostic trouble codes and perform self test.
  17. Disconnect all 4WABS harness connectors. Check 4WABS harness connectors for loose, pushed out or corroded terminals. Connect all disconnected 4WABS harness connectors and retest system. If problem still exists, replace 4WABS and perform data link test. See 4-WHEEL ANTI-LOCK BRAKE SYSTEM CONTROL MODULE  in REMOVAL & INSTALLATION. See DATA LINK DIAGNOSTIC TEST . If problem does not exist, system is operating normally. Clear all diagnostic trouble codes and perform self test.
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