Circuit Description

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Timing of combustion is accomplished by delivering a pulse of fuel into combustion chamber at a desired degree of cylinder travel. This desired degree (desired timing) defines current position of cylinder in relationship to top dead center. This test compares desired timing to measured timing when certain conditions are met. To retard injection timing, PCM extends stepper motor. To advance injection timing, PCM retracts stepper motor.

DTC will set when the following conditions are present:

Engine speed has not changed more than 56 RPM for 5 seconds.
A 5 degree difference between actual injection time and desired injection time exists.