DTC P0216: Injection Timing Control System: Description
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, 2002 Chevrolet RV Cutaway, and 2002 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
The timing of the combustion event is accomplished by controlling the beginning of injection measured in degrees of crankshaft rotation before Top Dead Center (TDC). This test compares the desired timing to the measured timing when certain conditions have been met. In order to retard the injection timing, the Powertrain Control Module (PCM) extends the stepper motor. In order to advance the injection timing, the PCM retracts the stepper motor.