Powertrain Controls - ECM/PCM

DTC 34 Injector Timing Stepper (ITS) Motor Circuit Fault:

Injection Timing Stepper (ITS) Motor Circuit Fault:

***This article was updated by TSB No. 51-65-28***

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) controls injection timing with the injection timing stepper motor. To increase injection timing the PCM extends the stepper motor. To retard injection timing the PCM retracts the stepper motor.

DIAGNOSTIC TROUBLE CODE (DTC) 34 WILL SET WHEN
^ Engine operating at steady RPM.
^ A 50 difference between measured and desired injection timing for 20.8 seconds.

ACTION TAKEN (PCM will default to)
None.

DTC 34 WILL CLEAR WHEN
The fault condition(s) no longer exist.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if DTC 34 is a hard failure or an intermittent.
2. This step checks for an open or short in CKTs 564 and 565.
3. This step checks for an open or short in CKTs 566 and 567.
4. The important thing in this step is that the PCM is sending a varying voltage (voltage will vary between 1 and 12), this will indicate that the PCM is OK and that there is a problem with the injection timing stepper motor. If there is a steady voltage present on any circuit, this will indicate a problem with the PCM or a circuit shorted to voltage.

DIAGNOSTIC AIDS
A hard start and possible poor performance condition might exist. Also measure injection timing will freeze at the point of the fault.