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Power & Ground Circuits (Frontier 3.3L & Xterra 3.3L)

  1. Start engine. If engine starts, go to step  6. If engine does not start, go to next step.
  2. Turn ignition off, and then on. Backprobing at ECM, measure voltage between ground and ECM harness connector terminal No. 24 (White/Blue wire) See Figure and Figure . If battery voltage exists, go to step  4. If battery voltage does not exist, go to next step.
  3. Check the following:
    • Check for poor, loose, corroded or damaged terminal connections at in-line harness connectors E74 and M82. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
    • Check for poor, loose, corroded or damaged terminal connections at in-line harness connectors M59 and F27.
    • Check for poor, loose, corroded or damaged terminal connections in fuse block junction connector E49.
    • Check fuse block fuses No. 13 (10-amp) and 27 (10-amp).
    • Check for open or short in circuits between ECM and fuse.
    If problem is found, repair as necessary. After repair, retest system.
  4. Turn ignition off. Disconnect ECM 124-pin harness connector. ECM is located below instrument cluster. Remove lower instrument panel to access ECM. See Figure. Check continuity between ground and ECM harness connector terminals No. 10, 19, 116 and 124 (Black/Red wire). See Figure. Check continuity between ground and ECM harness connector terminals No. 25 and 32 (Black/Yellow wire). Continuity should exist at all measurements. Also, check circuits for short to voltage. If problem is found, go to next step. If no problem is found, go to step  15.
  5. Check the following:
    • Check for poor, loose, corroded or damaged terminal connections in joint connector-2. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
    • Check for open in ground circuits between ground and ECM.
    If problem is found, repair as necessary. After repair, retest system.
  6. Turn ignition off. Backprobing at ECM, measure voltage between ground and ECM terminal No. 80 (Light Blue wire). See Figure. If battery voltage exists, go to step  8. If battery voltage does not exist, go to next step.
  7. Check the following:
    • Check for poor, loose, corroded or damaged terminal connections at in-line harness connectors M59 and F27. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
    • Check for poor, loose, corroded or damaged terminal connections in fuse block harness connector M27.
    • Check fuse block fuses No. 13 (10-amp) and 27 (10-amp).
    • Check for open or short in circuits between ECM and fuses.
    If problem is found, repair as necessary. After repair, retest system.
  8. Turn ignition on, and then off. Backprobing at ECM, measure voltage between ECM terminals No. 67, 72 and 117 (Black/Pink wires). Battery voltage should exist at each terminal for a few seconds after ignition is turned off. If battery voltage exists for a few seconds, go to step  14. If battery voltage does not exist, go to next step. If battery voltage exists after a few seconds, go to step  13.
  9. Disconnect ECM relay harness connector. ECM relay is mounted on bracket under instrument panel next to ECM. See Figure. Measure volage between ground and ECM relay harness connector terminals No. 2 and then No. 5 (Light Blue wires). See Figure. If battery voltage does not exist at both terminals, go to next step. If battery voltage exists at both terminals, go to step  11.
  10. Check for open or short in Light Blue wires between ECM relay and in-line harness connector F27. If problem is found, repair as necessary. After repair, retest system.
  11. Turn ignition off. Disconnect ECM 124-pin harness connector. ECM is located below instrument cluster. Remove lower instrument panel to access ECM. See Figure. Check continuity in Orange/Black wire between ECM harness connector terminal No. 4 and ECM relay harness connector terminal No. 1. See Figure and Figure . Continuity should exist. Also, check circuit for short to ground or short to voltage. If problem is found, repair as necessary. After repair, retest system. If no problem is found, leave ECM harness connector disconnected and go to next step.
  12. Check continuity in circuits between ECM harness connector terminals No. 67, 72 and 117 (Black/Pink wires) and ECM relay harness connector terminal No. 3. Continuity should exist. Also, check circuit for short to ground or short to voltage. If problem is found, repair as necessary. After repair, retest system. If no problem is found, leave ECM harness connector disconnected and go to next step.
  13. Working with ECM relay, apply battery voltage and ground to terminals No. 1 and 2. See Figure. When battery voltage is applied, continuity should exist between terminals No. 3 and 5. When battery voltage is removed, continuity should not exist. Replace relay, if test values are not as specified.
  14. Turn ignition off. Disconnect ECM 124-pin harness connector. ECM is located below instrument cluster. Remove lower instrument panel to access ECM. See Figure. Check continuity between ground and ECM harness connector terminals No. 10, 19, 116 and 124 (Black/Red wires). See Figure. Check continuity between ground and ECM harness connector terminals No. 25 and 32 (Black/Yellow wires). Continuity should exist. Also, check circuits for short to voltage. If no problem is found, go to next step. If problem is found, go to step  5.
  15. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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