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Home >> Nissan-Datsun >> 1993 >> Quest Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Code (DTC) Tests >> DTC 21: Ignition Signal

DTC 21: Ignition Signal

  1. Check Power Supply  - Turn ignition off. Disconnect ignition coil harness connector. See Fig 1. Turn ignition on. Measure voltage between ignition coil harness connector terminal "a" (White/Red wire) and ground. See Fig 3. If battery voltage is not present, repair wiring harness and/or connectors between ignition coil and ignition switch. If battery voltage is present, go to next step.
  2. Check Ground Circuit  - Turn ignition off. Disconnect power transistor harness connector. See Fig 1. Disconnect resistor/condenser harness connector. See Fig 2. Check continuity between ignition coil connector terminal "b" (Green wire) and following: power transistor connector terminal "i" (Green wire) and resistor/condenser connector terminal "d" (Green wire). See Fig 4. Check continuity between power transistor connector terminal "h" (Black wire) and engine ground. See Fig 5. If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.
  3. Check Input Signal Circuit  - Turn engine off. Leave power transistor and resistor/condenser wiring harness disconnected. Disconnect ECM harness connector. See Figure. Check continuity between resistor/condenser wiring harness connector terminal "c" (Red wire) and ECM connector terminal No. 3. 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 Output Signal Circuit  - Ensure ignition is off. Check for continuity between ECM terminal No. 1 and power transistor connector terminal "g" (Blue wire). See Figure and Fig 7 . If continuity is not present, repair harness or connectors as necessary. If continuity is present, go to next step.
  5. Check Components  - Inspect ignition coil, power transistor and resistor and condenser. See I SYS/COMP TESTS article in the ENGINE PERFORMANCE section. Repair or replace components if necessary and perform FINAL CHECK  in this article. If components are okay, repair ECM pin terminals and/or wiring harness connector.
Fig 1: Locating Ignition Coil & Power Transistor Harness Connectors
G93F80866Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Locating Resistor & Condenser Harness Connector
G93G80867Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: DTC 21, Checking Power Supply
G93H80868Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: DTC 21, Checking Ground Circuit
G93I80869Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: DTC 21, Checking Circuit Continuity
G93B80870Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: DTC 21, Checking Input Signal Circuit
G93C80871Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: DTC 21, Checking Output Signal Circuit
G93D80872Courtesy of NISSAN MOTOR CO., U.S.A.
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