Knock Sensor: Description and Operation

Knock Sensor Replacement:

Ignition Schematic:

Knock Sensor Cutaway View:

PURPOSE
The knock sensor detects abnormal vibration (spark knock or detonation) in the engine. This the PCM will use this information to determine proper spark advance and relay the appropriate trigger signal to the Ignition Control Module.


OPERATION
The sensor produces an Alternating Current (AC) voltage which increases with the severity of the knock. The knock sensor is specifically "tuned" to the engine based on the frequency of vibration that the engine creates when it knocks. The knock sensor for the 4.6L Northstar engine is tuned to 7000 Hertz. This signal is an input to the PCM, which then adjusts spark advance to reduce the spark knock.

LOCATION
The knock sensor is located on the rear cylinder bank of the engine block between cylinders 1 and 3 in the upper crankcase.