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Home >> Nissan-Datsun >> 1993 >> Sentra SE-R, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 2.0L >> Diagnostic Trouble Code (DTC) Tests >> DTC 21: Ignition Signal
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DTC 21: Ignition Signal

  1. Check Power Supply  - If vehicle does not start, go to step 5). If vehicle starts, turn ignition off. Disconnect ignition coil harness connector. See Fig 1 . Turn ignition on. Measure voltage between ignition coil harness connector terminal "a" (Gray/Yellow wire) and ground. See Fig 4 . If battery voltage is not present check wiring harness and connectors between ignition coil and ignition switch for open or short circuit. If battery voltage is present, go to next step.
  2. Check Ground Circuit  - Turn ignition off. Disconnect power transistor wiring harness connector. See Fig 2 . Check continuity between ignition coil connector terminal "b" (Black/Red wire) and power transistor connector terminal "e" (White wire). See Fig 5 . Check continuity between power transistor connector terminal "d" (Black wire) and engine ground. If continuity is present, go to next step. If continuity is not present, repair wiring harness or connectors as necessary and perform FINAL CHECK  in this article.
  3. Check Output Signal Circuit  - Turn engine off. Leave power transistor disconnected. Disconnect ECM harness connector. See Figure . Check continuity between terminal "c" (White wire) of power transistor wiring harness connector and terminal No. 1 of ECM wiring harness connector. See Figure and Fig 6 . If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.
  4. Check Components  - Inspect ignition coil and power transistor. See appropriate I - SYS/COMP TESTS article. Replace ignition coil and/or power transistor if necessary and perform FINAL CHECK  in this article. If ignition coil and power transistor are okay, repair ECM pin terminal(s) and/or wiring harness connector.
  5. Check Input Signal  - Perform this step if vehicle does not start. Ensure ignition is off. Disconnect ignition coil wiring harness connector. See Fig 1 . Leave resistor and condenser connected. See Fig 3 . Check continuity between ignition coil harness connector "b" and resistor/condenser connector terminal "f". See Fig 7 . Check continuity between ECM terminal No. "3" and resistor/condenser connector terminal "g". See Figure and Fig 7 . If continuity is present, go to next step. If continuity is not present, replace resistor and condenser.
  6. Check Components  - Inspect resistor and condenser. See I - SYS/COMP TESTS article. Replace resistor and condenser if necessary, and perform FINAL CHECK  in this article. If resistor and condenser are okay, repair ECM pin terminal(s) and/or wiring harness connector.
Fig 1: Locating Ignition Coil Harness Connector
G93A80929Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Locating Power Transistor Harness Connector
G93D80930Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: Locating Resistor & Condenser Harness Connector
G93E80931Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: Checking Power Supply
G93F80932Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: DTC 21, Checking Ground Circuit
G93G80933Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: DTC 21, Checking Output Signal Circuit
G93H80934Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: DTC 21, Checking Input Signal Circuit
G93I80935Courtesy of NISSAN MOTOR CO., U.S.A.
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