Symptoms of a Faulty Knock Sensor

Updated April 17, 2017

A car's power train control module, essentially the vehicle's engine control computer, receives various electronic signals from sensors responsible for regulating important functions. The knock sensor was designed as a listening device for the vehicle's engine. It is used to detect engine noises such as detonation, when fuel ignites in an engine's cylinder, as well as adjusts the ignition timing when the vehicle is being driven. When a knock sensor is not working properly, it may cause permanent engine damage. Therefore, there are various symptoms to aid in recognising a faulty knock sensor.

Check Engine Light

One of the main symptoms for a faulty knock sensor is the "check engine" light that will begin to flash on the vehicle's dashboard. This can be caused by the grade of gasoline being used; using cheap gasoline causes detonation and triggers the engine's main control board to wrongly diagnose the sensor. This will send a false malfunction message in the form of the check engine light. Before consulting a mechanic, try using a higher grade of gasoline. This can solve the problem.

Engine Noises

Sounds coming from the vehicle's engines are another sign of a faulty knock sensor. When the knock sensor is going bad, the driver may hear a pounding noise that becomes louder with time. This is caused by fuel and air igniting inside the cylinder instead of burning evenly before the sensor in its correct position, also known as pre-ignition.

Additional Symptoms

There are various other symptoms to determine a faulty knock sensor, such as fuel economy. The vehicle will use and burn more gas and require more frequent fuel replenishment, which will affect fuel economy. Detonation in the cylinders may cause strong burning smells coming from the engine, as well as exhaust smells.

Often, the vehicle will have trouble accelerating. Hesitation from the engine during acceleration may appear. Another common symptom is a vibration or misfire when the engine is being started, because of a sluggish engine.

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About the Author

Scarlett Gauthier began writing in 2003. Gauthier has a graphic design/arts DVS from Rosemount Technology Center in Montreal.