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Knock Sensor Replacement Service
What is the Knock Sensor all about?
The engine produces vibrations while running, and those vibrations change depending on how well the engine is running. When the engine is running poorly, often it can be corrected by adjusting the timing slightly. This is known as spark advance and retard. The knock sensor detects the vibrations in the engine and reports them back to the engine control module. From the frequency of the vibrations, the engine control module can advance or retard the timing to make the engine run smoother. The knock sensor is threaded into a hole in the engine block, cylinder head, or under the intake manifold. When the knock sensor isn’t operating properly, the engine will knock under load or when accelerating, and the Check Engine light will illuminate.
Keep in mind:
- The knock sensor is an electrical sensor. If it fails, it will need to be replaced.
- The symptoms of a faulty knock sensor are often misdiagnosed. A scan test can help isolate the failure without replacing unnecessary parts.
How it's done:
The vehicle is raised and supported on jack stands or the intake manifold is removed per manual as needed for access to the knock sensor.
The Knock Sensor is disconnected and unscrewed from the engine block.
The new knock sensor is installed, torqued to the correct specifications, and connected.
The vehicle is lowered off the jack stands or the intake manifold is reinstalled per manual.
The knock sensor is tested and the vehicle is road tested to ensure proper operation.
Our recommendation:
The knock sensor is commonly misdiagnosed as the symptoms related to it are similar to many other running problems. Have a mechanic check the codes in the engine control module to determine if the knock sensor is reading correctly. If there is a knock sensor-related code or the output from the knock sensor isn’t correct, the knock sensor needs to be replaced.
What common symptoms indicate you may need to replace the Knock Sensor?
- Engine knocks loudly especially at highway speeds or on acceleration
- Unexplained poor fuel mileage
- Decreased performance under load or on acceleration
- Check Engine light is on
How important is this service?
The knock sensor can cause the engine to run lean and hot if it is faulty, or it can run rich and burn excessive amounts of fuel. Driving your vehicle with a faulty knock sensor can lead to further repairs required from the symptoms if not addressed promptly.
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