I recently had one or both of the knock sensors in my '05 Toyota Highlander V6 go bad and I went to a mechanic to get both of them replaced. Some background: the check engine light came on and the accelerator felt like it had lost power. A diagnostic from the on-board computer confirmed that one or more of the knock sensors (apparently my vehicle has two) was not functioning properly.

The repair proceeded as normal and the knock sensors and some wiring and some gaskets were replaced, for a rather hefty price tag, as I fully expected. The mechanic also drained and refilled most of the fluids under the hood (transmission, power steering, motor oil, etc.). He mentioned while I was paying the bill that some or all of these fluids - he didn't say which ones specifically - had been exceptionally low, and explained that my knock sensor troubles were likely caused by the insufficient fluid levels.

Is it possible for low fluid levels to influence or cause problems with knock sensors? I was surprised to hear this because it was my understanding that knock sensors are entirely electronic components (though of course they function by listening for problems with non-electronic parts), and so it was my expectation that things like motor oil or transmission fluid didn't have anything to do with knock sensors, and certainly couldn't directly contribute to them becoming faulty. I assumed that my car was just old and beat-up - nearly 15 years young now, with more than 200,000 miles - and that knock sensors sometimes just wear out and need to be replaced, regardless of any preventive measures the driver might take such as always ensuring adequate fluid levels.

I'm no expert on vehicles, though, not even generally knowledgeable about them, and while I'd like to think I give my old car the regular maintenance it needs and pay close attention to fluids and sensors at all times, I can't exclude the possibility that something slipped by me. My most recent oil change before the check engine light came on was about 6 months and 3,000 miles prior, and I've never had any leakage issues that I've been aware of. I have no reason not to trust the mechanic's opinion that the fluid levels were related to the sensor going bad (in fact he was a super nice and seemingly super knowledgeable veteran of the industry, who quoted me $300+ less than the next lowest price I could find), but with my limited understanding of what's really going on under the hood I'm having a hard time grasping by what mechanism the two might be linked.

How might a deprivation of certain fluids directly or indirectly lead to failure of the knock sensor? Is there an obvious process or function I'm missing that could conceivably, with one or the other fluid being too low, cause the knock sensor to crap out early? What would that hypothetical scenario look like? I'm just curious how it all works, and I appreciate any and all feedback! Thanks.

1 Answer 1


Yes, it is possible that low fluid levels can cause sensors to fail prematurely.

One of the purposes of the fluid is to remove heat and if the sensor is then left to get too warm or overheated it can then fail or fail more rapidly.

This is one reason why the owner's manual suggest that you check the fluid levels regularly.

  • Also if the low fluid results in extra noise, that can lead to early knock sensor failure Oct 11, 2019 at 16:05

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