Engine Electrical
Knock Sensor
A knock sensor listens for engine knock, also called detonation, so the engine computer can retard timing and protect the engine. We carry 32 knock sensors from $14 to $146 for engines from 1994-2020, from Delphi, Standard Motor Products, AC Delco and Bosch, with fits for the Chevrolet Impala, Nissan Maxima and Honda Accord.
Shop knock sensor by vehicle
What the knock sensor does
Knock is fuel igniting at the wrong time, which makes a pinging or rattling sound and can damage pistons. The knock sensor is a vibration sensor bolted to the block. When it detects knock, the computer pulls back ignition timing until the knock stops.
Without a working sensor, many engines run with retarded timing as a safe default, which costs power and fuel economy.
Signs of a bad sensor
A failed sensor or wiring often sets a knock sensor code and turns on the check engine light. You may also notice pinging under load, sluggish acceleration or lower fuel economy.
On many V6 and V8 engines the sensors sit under the intake manifold, and damaged wiring is a common cause of codes. Inspect the harness and connector before replacing the sensor.
Fitting the right sensor
Match engine and year in the fitment table, and compare the part number and connector. The sensors listed here are sold without a wiring harness or mounting hardware.
Clean the mounting surface on the block and torque the bolt or stud to the specified value. Knock sensors are sensitive to mounting torque, and too loose or too tight can change their reading. Use the same type of mount as the original, without washers or thread sealant unless specified.
Knock Sensor questions
Can a bad knock sensor cause poor fuel economy?
Yes. Many engines retard timing when the sensor fails, which reduces power and fuel economy. Fixing the sensor or wiring can restore both. Clear the code and test drive after the repair.
Where is the knock sensor located?
It is bolted to the engine block or cylinder head. On many V engines it sits under the intake manifold, which makes replacement a bigger job.
Why does knock sensor torque matter?
The sensor reads vibration through its mount. Incorrect torque can make it too sensitive or not sensitive enough, which affects timing control. Use a torque wrench, not guesswork.