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Home >> GMC >> 1994 >> C3500 HD 7.4 N, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 6.5L Diesel >> DTC 34 - Injection Timing Stepper (Its) Motor Circuit Fault >> Notes
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DTC 34 - Injection Timing Stepper (Its) Motor Circuit Fault: Notes

The PCM controls injection timing with the injection timing stepper motor. To increase injection timing the PCM extends the stepper motor. To retard timing the PCM retracts the stepper motor. DTC 34 will set when:

  1. This step determines if DTC 34 is the result of a hard failure or an intermittent condition.
  2. This step checks for an open or short in the ITS coil 1 low circuit and the ITS coil 1 high circuit.
  3. This step checks for an open or short in the ITS coil 2 low circuit and the ITS coil 2 high circuit.