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My CEL came on and it was cleared out and determined to be my knock sensor. It stayed off for about 2 months and then in the last couple of weeks it's come back on for a couple of days and then gone back off. It's still currently off. How imperative is it to get this fixed soon? I have a 400 mile road trip coming up in a couple of weeks. Do I need it fixed before then?

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a knock sensor code will force the ECU into failsafe mode, meaning highly retarded timing. this will result in ultra rich fuel conditions, you will get 15 mpg vs the typical 25 mpg, etc, and power will be down.

 

It forces this to be pig rich to avoid any detonation and further damage.

 

Knock sensor is not something to go to the parts store for, and not something to get from a junkyard car or not to be bought used. they almost 100% have a failure rate after being 5 years old, the plastic casing gets brittle, and hard, and develops small cracks, that is when they fail.

Get new, from Subaru. should be between 45 and 75 bucks depending on year and model.

Edited by bheinen74

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I bought a knock sensor from Autozone last summer. Cost about $75, so I have to think that most parts stores can get you one.

 

It takes a wobbler on the end of a 3/8" drive to get to the awkward bolt that hold it in place on the block. It is a pretty ez job to do yourself, but it takes some patience to swap out. Just don't tighten new unit very tight, or you will break the plastic collar around the fastening bolt.

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oem from jason (Mike Scarff Subaru) for the 99 outback was 75 dollars, plus shipping. thats the wholesale price a dealer may sell for if you haggle.

 

Don't go aftermarket on this.

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