Q: Can a knock sensor keep my car from starting?

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I went to start my car for work yesterday and the AC as well as all the lights on the dash came on, but it didn't start. I had somebody come out to test the battery and it was fine. They plugged in their computer thing and the "knock sensor" code came up, but then the car started. Could the knock sensor keep it from starting? Is it dangerous to drive without fixing it? (I'm a struggling college student who was told it is $900 to fix it by Pep Boys and I definitely can't afford that).

My car has 102 miles.
My car has an automatic transmission.

Hello. A bad knock sensor will not keep your car from starting. The knock sensor’s purpose is to detect the sounds of pre-ignition in a running engine and convert it to a signal for the electronic control unit (ECU) so that the ECU can retard the ignition timing. The knock sensor could be missing entirely and it would not prevent your car from starting. You can drive with a bad knock sensor, but it could have adverse long term effects on your engine if there is a lot of pre-ignition, and the car will not pass most state inspections until it is fixed.

As for your starting issue, it sounds like you may have some sort of intermittent electrical failure, and if it has happened once, it will probably happen again. If this problem continues, it may be in your best interest to have an expert take a look at the vehicle in person. A certified professional from YourMechanic can come to your home or office to diagnose the starting problem and perform repairs as needed.

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