Knock Sensors - What Are They? How Do They Work?

What are they?

Ignition Knock Sensors monitor vibrations caused by engine knock or detonation.

How do they work?

A piezoelectric crystal generates a varying voltage based on engine vibration intensity, and sends a signal to the ECM. The vehicle computer then adjusts ignition and valve timing or injector pulse width for optimal engine performance.

Where are they located?

At the engine block, threaded into the side of the block or under the intake manifold.

Symptoms of failure

• Check engine light
• Engine hesitation
• Poor fuel economy
• Failed emissions test

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