My son's car threw this light a month ago--cleared it and has not been back

What will happen if it fails completely...what will the symptoms be?

Just trying to decide if it is crucial to change it out or just wait

thanks guys

I have the same motor as yours in my 99 Legacy. When it fails, the car will still be very driveable, however the computer will retard the timing, so horse power will be down, and gas millage will be lower.

 

Swapping out a knock sensor is not difficult, just arduous. Read the "search" feature on this forum to see instructions on how it is done. There will also be pictures on the write-ups to help you do the job.

usually just drives a little rough...sometimes in rare cases it can be very unpleasant to drive.

 

it's really easy to replace, cheap (ebay, even a member here sells them i think) and the plastic housing is cracked (that's how they always fail), best plan is to just replace it.

the one in my 97 GT was failing and the car had no power and crappy mileage even before it threw a code.

 

you can find them on EBAY for less than $20 delivered. they work fine. i don't know how long they last. mine is still good after 2 years.

 

the hard part is keeping the bolt in the socket when trying to insert it into the bolt hole. i use a bit of duct tape wrapped over the flange of the blot head. and i also use duct tape to attach the socket to the extension.

 

i also use a little dielectric grease on the bolt and the bottom of the sensor. it is easier to install with the air resonator box removed (96 - 99, ej25s) but you can do it with it in place. probably takes more time to remove the box than install the sensor.

Tip the knock senser grounds to its base file the base of senser to get good contact and file the block where it bolts up to get a good ground have had many set code when is poor ground

If you got a code for it, you'll end up with the ECU in failsafe which will cut ignition timing advance to prevent damage to the engine.

Typical symptoms are loss of power, misfiring, and/or lots of pinging. Ebay has new knock sensors cheap.