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

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

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:

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.

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