GM/Detroit 6.5L – Engine Management – TIMING CONTROL – INJECTION TIMING STEPPER (ITS) MOTOR

Description
The injection timing stepper motor is located on the right side of the injection pump. The motor housing contains two coils that are controlled by voltage from the PCM. (See the “Fuel Control” section for a description of stepper motor mechanical
and hydraulic operation.)

ITS Circuit Operation
The injection timing stepper motor contains two coils that control injection pump timing. The PCM controls these coils through four circuits (figure 5-40):
• CKT 564 for coil 1 low position
• CKT 565 for coil 1 high position
• CKT 566 for coil 2 low position
• CKT 567 for coil 2 high position

DTC 34 — “Injection Timing Stepper (ITS) Motor Circuit Fault”
DTC 34 sets when engine RPM is steady and the PCM detects injection timing that is a 5-degree difference between “Desired Injection” and “Measured Injection” timing.