Circuit Description

Timing of the combustion event is accomplished by delivering a pulse of fuel into the combustion chamber at a desired degree of piston travel. This desired degree (desired timing) defines the current position of the piston in relationship of top dead center (TDC). This test compares desired timing to measured timing when certain conditions have been met. To retard injection timing, the powertrain control module (PCM) extends the stepper motor. To advance injection timing the PCM retracts the stepper motor. This is a type B diagnostic trouble code (DTC).