Knock Sensor: Description and Operation

PURPOSE
The knock sensor is used to detect engine detonation (ping). The ECM/PCM will retard the electronic spark timing based on the signal received.

OPERATION
The knock sensor internal circuit causes the ECM's/PCM's 5 volts to be pulled down to about 2.5 volts. The knock sensor produces an A/C signal which rides on the 2.5 volts DC signal. The amplitude and frequency are dependent upon the knock level.

LOCATION
Engine block near exhaust manifold.