DTC 34, Injection Timing Stepper (Its) Motor Circuit Fault: Notes

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

• Engine operating at steady RPM.
• A 5 degree difference exists between measured and desired injection timing for 20.8 seconds.
  NOTE: Test numbers refer to numbers on diagnostic chart.

1. This step determines if DTC 34 is result of a hard failure or an intermittent condition.
2. This step checks for an open or short in ITS coil 1 low circuit and ITS coil 1 high circuit.
3. This step checks for an open or short in ITS coil 2 low circuit and ITS coil 2 high circuit.
4. The importance of this step is that PCM is sending a varying voltage between 1-12 volts indicating PCM is okay and that problem is with injection timing stepper motor. A steady voltage present on any circuit indicates a problem with PCM or a circuit is shorted to voltage.