BMW 320i xDrive Knock Sensor Replacement Cost

Know what price you should pay to get your vehicle fixed.

Knock Sensor Replacement
The average cost for a BMW 320i xDrive knock sensor replacement is between $319 and $446. Labor costs are estimated between $193 and $245 while parts are priced between $126 and $201. Estimate does not include taxes and fees.
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What is a knock sensor?

A protective device, the engine knock sensor alerts the driver that knocking has been detected inside the engine.

How does the knock sensor work?

Every time a vibration is sensed by the engine knock sensor, it sends a signal to the computer, reporting how large of a vibration was present. The engine computer is programmed to expect a specified range of signals from the engine knock sensor. This range allows the knock sensor enough precision to pick up the smallest vibrations, without triggering an erroneous warning. Most information from the knock sensor will be bumps in the road or closing the vehicle's door. However, when a vibration is large enough, the knock sensor signal will trigger the computer to alert the driver. This is a protective measure installed on engines to prevent complete engine failure when a detected harmful event occurs.

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What are the symptoms related to a bad knock sensor?

When the knock sensor sends a warning signal to the vehicle's computer, the computer in most modern vehicles will simultaneously reduce power output, send a warning message to stop the engine immediately, and the illuminate the check engine light. On-board diagnostics (OBD) trouble codes will be stored, and will reference the engine knock sensor. When turned off, some vehicles will not restart until the knock sensor OBD code is cleared, and may shut off immediately if the code recurs after reset.

»MORE: How to tell if you have a bad knock sensor

Can I drive with a knock sensor problem?

When the knock sensor sends a warning signal to the computer, it is always treated as if there is an internal engine failure. The vehicle should not be started or driven unless the knock sensor is diagnosed as faulty. If there is an internal failure occurring, starting the vehicle can exacerbate that failure.

How often do knock sensors need to be replaced?

Specific vehicles have earned reputation for knock sensor failure, but that hardly speaks for all engines. The knock sensor is tough enough to last an average of over 150,000 miles mounted onto the engine.

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How are knock sensor issues diagnosed?

The check engine light and knock sensor related OBD codes will immediately send a technician to test the knock sensor and knock sensor circuit. The technician will first conduct a visual inspection of the sensor and associated wiring, and note any observed issues. If the knock sensor wiring harness and electrical connectors are working properly, the technician will test the knock sensor. Once the technician suspects the knock sensor, they may decide that removal for further bench testing is warranted, or the diagnosis has been confirmed. After the round of testing is complete, any failed component must be replaced, and the vehicle will be tested to ensure the customer complaint does not return.

Knock Sensor Replacement Cost Estimates

The average cost for a Knock Sensor Replacement is between $319 and $446 but can vary from car to car.

How is a knock sensor replaced?

If the knock sensor is faulty, the technician will unscrew the sensor, and install the new sensor. There is normally only one electrical connector per knock sensor, and there may be another knock sensor on the engine. If the oil must be drained to change the knock sensor, the oil filter may be recommended to be changed as well.

RepairPal Recommendations for knock sensor issues

We always recommend contacting the dealership parts department for revised part numbers. There may be a new part number for the engine knock sensor, which can be a redesigned part that fixes known flaws. Aftermarket sensors may not have these updates,

What to look out for when dealing with knock sensor issues

Some vehicles are well known for knock sensor issues, but knock sensors on those vehicles should still be tested before replacement, or vehicle operation. There are many types, grades and certifications for engine oils. Before adding oil to the engine, the required oil specifications must be known. Consulting the owner's manual for your vehicle is the best way to ensure you have the correct type, grade and certifications. If improper oil is added, contact one of your local certified shops to discuss the situation. Depending on the amount added, it may be safe to operate as normal, or unsafe to start and run.

Can I replace the knock sensor myself?

Most people can replace a knock sensor, and very few basic tools are needed, but diagnostics, on the other hand, may be a different story. It is vital that the sensor is diagnosed correctly. If the sensor is erroneously blamed for the fault, the component causing the knocking may be further damaged when the engine is restarted. If diagnosing the switch proves difficult or impossible, the best idea is to contact a professional.