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ECM Power & Ground Circuits (Quest)

  1. Turn ignition on. Measure voltage between ground and ECM harness connector terminals No. 38 (Red/Black wire), No. 47 (Red/Black wire) and No. 109 (Red/Black wire). See Figure and Figure . ECM is located behind glove box. Battery voltage should be present. If battery voltage is present, go to step 3). If battery voltage is not present, go to next step.
  2. Turn ignition off. Disconnect ECM harness connector. Check continuity between ground and ECM harness connector terminals No. 6 (Black wire), No. 13 (Black wire), No. 107 (Black wire), No. 108 (Black wire) and No. 116 (Black wire). Continuity should exist. If continuity does not exist, repair harness or connectors. If continuity exists, check ECM pin terminals and ECM harness connector terminals for damage or corrosion.
  3. Turn ignition off. Disconnect ECM harness connector. Disconnect ECM (ECCS) relay. Relay is located in fusible link box next to battery. Check continuity between ECM harness connector terminals No. 38 (Red/Black wire), No. 47 (Red/Black wire) and No. 109 (Red/Black wire) and ECM relay connector terminal No. 5 (Red/Black wire). See Figure . Continuity should exist. If continuity exists, go to next step. If continuity does not exist, check harness and connectors between ECM and ECM relay.
  4. Measure voltage between ground and ECM relay harness connector terminals No. 1 (Red wire) and No. 3 (Red wire). See Figure . Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage is not present, check 25-amp fusible link. Check harness and connectors between ECM relay and battery.
  5. Check continuity between ground and ECM harness connector terminals No. 39 (Black/Red wire) and No. 48 (Black/Red wire). Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open in harness or connectors.
  6. Check continuity between ECM harness connector terminal No. 4 (White/Green wire) and ECM relay harness connector terminal No. 2 (White/Green wire). See Figure . Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open in harness between ECM harness connector and ECM relay harness connector.
  7. Turn ignition on. Measure voltage between ground and ECM harness connector terminal No. 36 (Blue/Yellow wire). Battery voltage should be present. If battery voltage is present, check ECM relay. See RELAYS under RELAYS & SOLENOIDS  . If relay is okay, check ECM pin terminals and ECM harness connector terminals for damage or corrosion. If battery voltage is not present, check harness and connectors. Check 10-amp fuse. Check harness and connectors between ECM and ignition switch.
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