Is a knock sensor necessary?

My check engine light is on and I took it to autozone and they said it was a knock sensor. Is it necessary to replace it if I put 93 octane gas in there. I noticed knocking before when I was putting 87 octane in, but it seems to have stopped since putting premium in. I am a 96 subaru legacy.


meant to say I have a 96 legacy, not I am.

3 Answers

  • Nick
    Lv 4
    1 decade ago
    Favorite Answer

    How much is a knock sensor?

    You are paying an extra $0.20 per gallon for fuel now and can't utilize the extra octane most of the time.

    If the light stays on, you should replace the sensor even if the car runs good because when something else fails you will not know until you notice other symptoms like mpg dropping off or misfire, etc.

    • Login to reply the answers
  • 4 years ago

    Maxima's have always had very high strung engines when it comes to maintanence and the type of fuel you use. Let's break this down for you. A knock sensor is one of the many sensors in your car that tell your ecu how the engine is running. It's a phonic sensor that picks up irregular sounds that can be harmful to your engine. Low octane gas in your car will cause your car to knock and can even cause catostrophic engine damage, which I've seen more than once. My first assumption would be that the gas you're putting into your car would cause your engine to detonate(alarm the knock sensor), however, that would bring up several different trouble codes(check engine light). So if your ecu has stored knock sensor codes, I'd go ahead and check them out. Your mechanic may let the car idle and tap on them slightly to see if the engine idle is affected or not. Your car should stumble because tapping a knock sensor is simulating a badnoise(knock or detonation or ping) which will make your ecu go rich or retard timing(make it safe for that period).

    • Login to reply the answers
  • 1 decade ago

    yea it controls timing

    • Login to reply the answers
Still have questions? Get your answers by asking now.