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Home >> Infiniti >> 1993 >> G20 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Code (DTC) Testing (G20) >> DTC 21: Ignition Signal
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DTC 21: Ignition Signal

  1. Check Power Supply  - Start engine. If engine starts, go to step 5). If engine does not start, turn ignition off. Disconnect ignition coil harness connector. Turn ignition on. Measure voltage between ignition coil harness connector terminal "a" (Black/Red wire) and ground. See Fig 1 and Fig 2 . If battery voltage is present, go to next step. If battery voltage is not present, check Black/Red wire circuit continuity between ignition coil and ignition switch.
    Fig 1: Locating Ignition Coil Harness Connector
    G93C78495Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 2: DTC 21, Checking Power Supply
    G93D78496Courtesy of NISSAN MOTOR CO., U.S.A.
  2. Check Ground Circuit  - Turn ignition off and disconnect power transistor harness connector. Verify harness continuity between ignition coil connector terminal "b" and power transistor connector terminal "e" (Green/Yellow wire), and between power transistor connector terminal "d" (Black wire) and engine ground. See Fig 3 and Fig 4 . If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.
    Fig 3: Locating Power Transistor Harness Connector
    G93E78497Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 4: DTC 21, Checking Ground Circuit
    G93F78498Courtesy of NISSAN MOTOR CO., U.S.A.
  3. Check Output Signal Circuit  - Turn ignition off and disconnect ECM harness connector. Verify harness continuity between ECM terminal No. 1 and power transistor connector terminal "c" (White wire). See Fig 5 . If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.
    Fig 5: Checking Output Signal Circuit
    G93G78499Courtesy of NISSAN MOTOR CO., U.S.A.
  4. Check Component  - Inspect ignition coil and power transistor. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Replace ignition coil and/or power transistor if necessary and perform FINAL CHECK  .
  5. Check Input Signal Circuit  - Turn engine off. Disconnect ignition coil harness connector and resistor and condenser 4-pin connector. Disconnect ECM harness connector. Verify harness continuity between ignition coil connector terminal "b" and resistor and condenser connector terminal "f" (Green/Yellow wire), and between ECM terminal No. 3 and resistor and condenser connector terminal "g" (Yellow/Red wire). See Fig 6 and Fig 7 . If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.
  6. Check Component  - Inspect resistor and condenser. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Replace resistor and condenser if necessary and perform FINAL CHECK  .
Fig 6: Locating Resistor & Condenser Harness Connector
G93J78500Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: DTC 21, Checking Input Signal Circuit
G93A78501Courtesy of NISSAN MOTOR CO., U.S.A.
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