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Home >> Infiniti >> 1993 >> J30 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Code (DTC) Testing (J30) >> DTC 21: Ignition Signal

DTC 21: Ignition Signal

  1. Start engine. If engine does not start, go to next step. If engine starts, go to step 3) or to step 4).
  2. Check Ground Circuit  - If engine does not start, turn ignition off. Disconnect Power Transistor Unit (PTU) harness connector. Verify harness continuity between PTU harness connector terminal "d" (Black wire) and engine ground. See Fig 1 -Fig 5 . If continuity is present, go to step 4). If continuity is not present, repair harness or connectors as necessary and perform FINAL CHECK  .
    Fig 1: Locating Ignition Coil Relay
    G93F78522Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 2: Locating Ignition Coil Harness Connector
    G93G78523Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 3: Locating Power Transistor Unit Harness Connector
    G93H78524Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 4: Locating EFI Harness Connectors
    G93I78525Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 5: DTC 21, Checking Ground Circuit
    G93J78526Courtesy of NISSAN MOTOR CO., U.S.A.
  3. Search For Malfunctioning Circuit Using CONSULT  - Turn ignition off and connect CONSULT. Perform POWER BALANCE in ACTIVE TEST mode with CONSULT. Search for circuit which does not produce a momentary engine speed drop.
  4. Check Output Signal Circuit  - Turn ignition off. Disconnect ECM harness connector and PTU harness connector. Verify harness continuity between ECM harness connector terminals and PTU harness connector terminals as follows:
    • ECM terminal No. 1 and PTU terminal "g" (Yellow wire).
    • ECM terminal No. 2 and PTU terminal "f" (Light Green/Black wire).
    • ECM terminal No. 3 and PTU terminal "e" (White wire).
    • ECM terminal No. 11 and PTU terminal "c" (Pink/Black wire).
    • ECM terminal No. 12 and PTU terminal "b" (Red/Blue wire).
    • ECM terminal No. 13 and PTU terminal "a" (Gray wire).

    See Fig 6 . If continuity is present, go to next step. If continuity is not present, verify harness continuity between ECM connector and PTU connector. Repair harness or connectors as necessary.

  5. Check Component  - Inspect power transistor unit. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Replace power transistor unit if necessary and perform FINAL CHECK  .
Fig 6: DTC 21, Checking Output Signal Circuit
G93A78527Courtesy of NISSAN MOTOR CO., U.S.A.