Knock Sensor: Description and Operation

PURPOSE
The knock sensor is used to detect engine detonation (ping). The PCM will retard the electronic spark timing up to 15 degrees based on the signal received.

LOCATION
Engine block near exhaust manifold.

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