Knock sensor warning problems

Well only a few days into having a Subaru and I’m having problems so I need some help. I bought myself a ’95 jap import wrx wagon and I’m having a problem with the check engine light coming on. When I start the car first nothing shows up but after about 30 mins of drive the light comes on. I ran a diagnostic on it and found it was giving me a 22 which is the knock sensor warning. The car runs perfectly when the light is off but would hesitate slightly on boost when it comes on, haven’t been driving it hard once the light comes on. Even with the light on the car idles smooth as anything no noises or anything. I thought first it could have been bad fuel so I reset the ECU and filled it up with E5 but the light still comes on when fully warmed up. The cars been in the country for the last 9 years and I was told it was run on regular 95 ron so I guess it was remapped at some stage. Is it possibly that it’s a genuine knock sensor warning if so what issues but fuel could cause this? Or what are the chances of it being a faulty sensor? I was thinking of trying an octane booster just to totally eliminate a fuel issue but where should I go from there. Cheers for any help lads it’s never nice getting a problem with a car you just bought.

Its more likely to be a faulty knock sensor alright. There was only 98 octane fuel available in Japan when your car was made so if you're running E5 in theory you shouldn't have a problem.

I have heard of knock sensors going faulty too. Give one of our traders a call & I'm sure they'll sort you out.

As above

And the reason it hesitates with the light on is because the ecu is going into safe mode

Thanks lads cheers for that I'll try that and hopfully it will do the trick.

ask the last owner has this just started or has it been a fault in the car since you got it...i had the same problem with a wrx...the problem was a mate had removed a rsm and had crossed wires at the ecu..car was running perfect ontil it hit 4500revs when fully warmed up and had no other problem..fixed the wires at the ecu and problem solved,have you been at the ecu..if so id go back and have a good look at it first.

Cheers for that jwc, I haven't been near the ECU only reset it after the light was coming on I'm going to try change the knock sensor first and see from there what happens.

Well just an update on this issue for anyone having the same one. It turned out to be a dodgy knock sensor so I replaced it and all is sorted. Straight forward job to do but you will need a long extension bar for your ratchet, I just removed the intercooler and if you look down the right side of the engine as your looking into the bonnet, at the back just left of the idle control valve about 6 inches down you’ll see the knock sensor bolted straight down onto the block. Use the long extension bar and ratchet and remove the bolt that goes through the sensor and holds it to the block. Just remember which way the sensor is sitting as the new sensor has to sit in the same position. You won’t be able to get the sensor out with your fingers I just used the wire from the sensor and disconnected it from the connection which is about 6 inches from the sensor and pulled it out with that. Putting in the new one I just put the bolt through the sensor and dropped the sensor into position it’s a bit tricky but you’ll get it. Don’t know how clear that is but anyway that’s it. Thanks for the helps lads.

Good to hear a sucess story for once-good man Adam

glad ya got sorted man fair play

Howdee All, Have had this light pop on a few times with me but with no missing or hesitation or anything. I was talking to the previous owner and he said that it was got to do with the downpipe being changed and the larger TD06 Turbo that the sensor is picking up its running different. Is this possible?