Circuit Description

The Knock Sensor (KS) is used to detect engine detonation and is located below intake manifold. KS is a piezoelectric element which generates an AC signal when vibrated. Normal engine operation will cause KS to generate a signal of a certain known frequency. When engine knock is present, KS frequency changes which signals PCM to retard ignition timing. By retarding ignition timing, engine detonation detected should be reduced. DTC will set when engine speed is 1200 RPM or greater, VSS and TP sensor indicate that the vehicle is accelerating.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in FREEZE FRAME buffer. PCM will default to maximum spark retard.