right well the C/E light has been coming on and of randomly.. occasionally staying on and sometimes going off with a rev of the engine.., done a code check and its come up with 22 knock sensor, the car never feels any different if light is on or off
tried to reset the ecu but i think i have a missing wire on 1 of the green connectors...1 has only 1 wire coming out, so no joy when i tried.
is there an alternative way to reset the ecu?
car is an impreza 555 GT (n plate). mods (if it matters) are stainless to the turbo stainless mani, headers, and a chip, also just had a stage 2 carbon kevlar clutch (sure ive heard something about racing clutches occasionally throwing the knock sensor on... may be a load of poop tho....
anyway any input wud be great folks

 

disconnect your battery for 10 mins or so thats what i did today to clear my codes mate...

 

£42 gets you a new knock sensor worst case!

 

will do that right now, thanks pal, after talking to a tuner im thinking the knock sensor might be on its way out... would explain the light coming on and off

 

BUT... what if the K/S is correct... how would i know?, in all honesty theres about 20-30 secs of piston slap first thing in the mornin, goes away after that... related?, or wud i know all about it if there was knock as such

 

with ignition off disconnect plug from knock sensor with a multimeter measure the resistance between cars body (as earth) and knock sensor terminal pin 1 i think, should be about 560 ohms..:-)

 

http://rapidshare.com/#!download|159...reza.pdf|49709

 

grab yourself the 93-96 workshop manual from the link above really hand.. tells you how to check everything top to bottom matey

 

The knock sensor is there to detect pre-ignition of the fuel/air mix ('det') and when it is working correctly and detects 'det' it will retard the timing which you may feel as the car holding back slightly under acceleration. This will only happen when you are giving it some stick (certainly not when you say there is a bit of piston slap on startup) and a CEL won't be generated.
Chances are the sensor is faulty or the earth for it to the block is bad, so safe bet is to fit a new one ( intercooler off, fiddly job anyway, and make sure the aluminium on the block where it contacts is clean).

Kevin

 

excellent cheers dudes, ill pick 1 up asap, really paranoid about this impreza.. had a few , some good but the last 2 not so good and vowed them to be my last, but couldent stay away and this 1 is a minter from belgium, but now rhd... just hope this is nothing serious

 

The knock sensor on my old car packed up at 80k miles and 7 years with the same symptoms you have. There was some minor oxidation on the block and some rust on the sensor surface, car ran fine. New sensor, no more errors.

 

oxidation.. like kinda blue/green spots that just wipe away? if so i have a little of that? (or just made myself sound a **** lol)

 

Green oxidation usually occurs on electrical contacts.

On the aluminium block it is usually a white powder.

 

yea that sounds like it.... so that is related to the dodgy knock sensor then?, will order a K/S tonight and fingers crossed no damage has been done or is there

 

ive had exactly the same problem but the CEL dose illuminate whilst the engine feels 'held back'. would using octane booster to illiminate the engine from knocking confirm that its the sensor at fault?

 

Don't quote me though, I'm no chemist.
Although I am fairly confident a new sensor will solve your problem.

 

that'll do for me, ive just reset the ecu and will take it a little run later... if its an old code and now off then happy days, if not knock sensor. cheers for all the info dudes

 

Fingers crossed a simple reset will do the job, if not, i have a Knock Sensor i have one here if you are interested?

 

cheers mate, ill have that if the light is not cleared

ps cheers for the link to the service manual, very handy

 

When my sensor had an intermittent fault I replaced it fairly quickly and didn't cane the car with the faulty sensor on there so I can't tell you what would happen if the sensor failed whilst you were giving it some beans.
It wouldn't surprise me if the ecu acted on a faulty sensor signal to protect the engine though.
You haven't said if your error is code 22 however.

 

pretty sure if the knock sensor goes altogether ecu should hit limp mode happened to a friends subi a few years ago.. £42 get it new..lol

 

i pluged it in to a snap on EOBD scanner we have in work but it wouldnt communicate. took it to the auto electrition we use and plugged it into his bosh scanner, it did flag up a past code relating to the knock sensor but no present codes.

 

only had the scoob hit limp mode once and was when the speedo cable snapped! (different car), good to know that tho, it will be all sorted shortly .... hopefully

 

andy if its a classic like mine just use the diagnostic plugs under the steering wheel and count the flashes matey

 

its year 2000 on a Y reg sport (non turbo unfortunatly) dont think its the flasher type, just my luck to pursuade my boss to invest in a decent scanner and it wont communicate with myne

 

right.... disconnected the battery for about 30 mins, code was on still... stayed on for 15 mins of driving then went off and stayed off for about 15 mins... parked up and left it, light didnt come back on... what you think?