What symptoms will appear if the knock sensor is broken?

[OwenMarie]

Cars with a faulty knock sensor will exhibit the following conditions: engine shaking, noise generation, the malfunction indicator light will illuminate, and in severe cases, it may lead to significant damage to the firmware. Below are the reasons related to a faulty knock sensor: 1. Early ignition, poor exhaust gas recirculation: Engine knocking caused by low-grade fuel and other reasons can result in engine damage. The knock sensor provides the knocking signal to the computer (some through the Powertrain Control Module PCM), allowing the computer to readjust the ignition timing to prevent further knocking. 2. The knock sensor is placed in different locations on the engine block or cylinders: When vibration or knocking occurs, it generates a small voltage peak; the greater the knocking or vibration, the larger the peak produced by the knock sensor. A certain high frequency indicates knocking or vibration, and knock sensors are typically designed to measure frequencies in the range of 5 to 15 kHz.

[StErin]

Last time I drove my old car, the knock sensor failed, and the car started acting up. The check engine light suddenly came on and kept flashing, as if warning me of a problem. The car had no power when accelerating, like it was dragging its feet, and there was no response even when I floored the gas pedal. Sometimes, I could hear a knocking sound, especially when going uphill or driving fast, which was quite annoying. The fuel consumption also increased—previously, a full tank could last 500 kilometers, but now it only gets around 450. What worried me the most was that with the sensor broken, the engine couldn't adjust the ignition timing on its own, which might damage internal parts. If left unfixed for a long time, it could cost even more to repair. So as soon as I noticed something was wrong, I immediately took it to the repair shop. The mechanic scanned the trouble codes with a tool and replaced the sensor, fixing the issue. For safe driving, don’t wait until the symptoms get worse—address them early.

[DeAdam]

As someone who frequently deals with cars, I've observed many cases where a faulty knock sensor causes noticeable symptoms. The most common is reduced engine performance and weakened power output—the car feels sluggish and struggles to overtake. The ECU (Engine Control Unit) detects the abnormality, triggering the check engine light and activating protective measures—such as retarding ignition timing to prevent engine damage from knocking. Simultaneously, fuel consumption increases due to lower efficiency, and you may feel engine vibrations or hear knocking sounds while driving. If left unrepaired, excessive carbon buildup can shorten the engine's lifespan. I recommend checking sensor connections during routine maintenance and seeking professional repair immediately if issues arise to prevent minor faults from escalating.

[JulietFitz]

In my many years of driving, the knock sensor has failed several times, with very obvious symptoms: the car acts like it has a cold, the engine shudders after starting, acceleration is weak, and there's a sound of poor fuel combustion. The check engine light coming on is a signal, and fuel consumption quietly increases. It needs to be fixed promptly to avoid internal engine damage.