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Home >> Nissan-Datsun >> 1994 >> Sentra SE-R, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Engine Controls - Tests W/Codes - 1.6L) >> Diagnostic Trouble Code (DTC) Tests >> DTC 21: Ignition Signal
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DTC 21: Ignition Signal

WARNING: This page is about a different variant/trim than selected.
  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 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 engine ground and ignition coil connector terminal "d" (Black/Red wire). Check continuity between engine ground and power transistor connector terminals "b" (Black wire) and "e" (Green/Yellow wire). See Fig 5 . 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 5 . 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 SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. 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. 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". If continuity is present, go to step 4). If continuity is not present, replace resistor and condenser.
Fig 1: Locating Ignition Coil Harness Connector (Sentra)
G93C80897Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Locating Power Transistor Harness Connector (Sentra)
G93D80898Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: Locating Resistor & Condenser Harness Connector (Sentra)
G94J44486Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: DTC 21, Checking Power Supply (Sentra)
G93H80900Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: DTC 21, Checking Ground Circuit (Sentra)
G93I80901Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: DTC 21, Checking Output Signal Circuit (Sentra)
G93J80902Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: DTC 21, Checking Input Signal Circuit (Sentra)
G93A80903Courtesy of NISSAN MOTOR CO., U.S.A.
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