What Is a Knock Sensor?

If you feel an unusual knocking in your car, especially at high speeds, the problem may be a faulty knock sensor. This is an important engine part that serves two main purposes.

Identification

A knock sensor is a knob-like part that is linked to the car's engine. As the name implies, it senses knocks in the engine. Wells Manufacturing, a company that produces knock sensors, likens the sound of an engine knock to marbles against metal.

Monitoring

One of the purposes of a knock sensor is to monitor the performance of the engine. If there is a problem, the knock sensor will send a signal to the PCM (Powertrain Control Module--the car's computer).

Protection

Knock sensors also protect car parts from the damaging effects of engine knock. When a knock sensor is bad, it can't regulate the engine properly. The car vibrates and it sounds like there is something banging up against the car's cylinder. The knocking action can destroy the pistons, rods, valves, gaskets and plugs.

Gas Mileage

A knock sensor is important to a car's fuel efficiency. It helps the car balance its timing and fuel-to-air mix, which optimizes the amount of power to the engine.

Considerations

Failure to replace a bad knock sensor over an extended period of time can possibly lead to extensive and expensive damage to the engine.

References

• Knock Sensors Do Two Jobs
• Knock Sensor Description
• Powertrain Control Module (PCM)

Resources

• About the Knock Sensor Trouble Code