What does a knock sensor do?

Knock is a characteristic noise produced by the engine as a result of poor design, improper use, or incorrect tuning. It's a rattling sound that results from the ignition of gasoline. In other words, the resonance is caused by the explosion of the fuel in the cylinder before combustion is initiated by the spark plug. The knock sensor monitors the combustion process in the engine. This article will tell you everything you need to know about the knock sensor.

What is a knock sensor?

The knock sensor detects vibrations on the engine block and tells the engine control unit (ECU) to increase the ignition delay to suppress knocking.  Its signal helps the engine management system prevent knocking combustion, thus preserving engine mechanics.

How does a knock sensor work?

Gasoline engines are equipped with an ECU. This optimizes fuel combustion by defining the correct ignition angle for the ideal combustion of the air-fuel mixture. Occasionally, depending on how the engine is used (load, temperature, and rpm), self-ignition may occur, resulting in a knock.

The knock sensor "listens" to the structural vibrations of the engine block.  Generally based on piezoelectric technology, engine vibrations are converted into an electrical signal that is received and decoded by the ECU to determine if a knock is present.

The signals are filtered and analyzed by the ECU. The knock signal is assigned to the appropriate cylinder. If a knock is present, the ignition signal for that cylinder is retarded until the combustion process is free of abnormal noise.

Where is the knock sensor located?

The knock sensor is installed directly on the engine block of your vehicle. It is secured with bolts.

How can I tell if my knock sensor is working properly?

There are many signs that my car or certain parts are damaged or malfunctioning. If your knock sensor isn't working properly, the MIL light on your dashboard will come on.  Your car's engine may not be working properly.

If this is the case, you'll need to have your vehicle inspected. OBD fault codes such as P0335 and P0324, related to the knock sensor, are likely to appear during the vehicle diagnostic process. Codes P0327 and P0328 indicate an open or short circuit in the sensor's signals to the ECU.

As a result of this failure, you'll notice a sharp increase in fuel consumption, and your vehicle may go into degraded mode. This electronic safety device limits your engine's power and performance to prevent collateral damage.

How much does a sensor cost?

Replacement by a home mechanic takes 30 minutes, depending on location, and costs between $30 and $130, depending on the vehicle.

Our electronic sensor maintenance tips

This is a durable piece of equipment that doesn't require maintenance as such. However, certain precautions must be taken to avoid damaging this part. Ensure that the sensor is securely fastened to the engine block. Observe the manufacturer's recommended torque when tightening this component. Use a torque wrench during installation.