i have a uk 99wrx which keeps flashing knock sensor and pressure sensor faults. i have had them both changed by subaru themselves but the problem still seems to arise, and the car becomes very jumpy and seems to behave irratically. hellllp please?

 

i would take it back to main dealer, if they have miss diagnosed the problem then its upto them to sort it.

 

its strange i took it to them 4 months ago and they changed the knock sensor. it was fine for the first week but then started reading the same faults again so i took it back to subaru and they changed the knock sensor for a second time free of charge and said the pressure sensor was fine. 4 months later its playing up worst than ever,i was driving earlier below 3000 rpm in 3rd gear and it started kangerooing up the road so i pulled over switched off and waited 3 mins started it up and the check engine light didnt come on again but the car still wasnt right. i dont really know if subaru will be able to diagnose it will there fault reader alone.

 

You know you can read the codes yourself?

 

yes i have done that today and read them and also reset my ecu manually. i might look at changing the ecu incase its bugged.

 

if the ecu was buggered i dont even think the car wud start but check all boost pipes etc are all on incase 1 of them has been pulled off accidently

 

i have checked all the boost lines also my dump valve is all good. the strange thing is it only does it when i have a heavy passenger. ie my 17 stone mate lol.

 

if your car is heavier then the turbo is having to spin more to pull weight an use more boost so somethin to do with something down them lines which cud even mean pressure sensor but ive never had a scooby to do this yet. do u check ecu faults when the engine light is on

 

As Seddomyster says, ECUs tend to either work fine or not at all, it'd be unusual (although not totally impossible) for a subtle fault of the sort you're reporting to be caused by a fault within the control unit.

There is also a certain amount of truth to the idea that the car will work harder with a fatso in the passenger seat than it will with you there on your own.

However, the other thing that occurs to me is that the ECU is located in the passenger footwell. If the problem *only* presents when Mr Pies is in the car with you, is it possible he has a habit of shoving his feet hard into the footwell to brace himself? It shouldn't be an issue, especially if you have the standard metal cover bolted on top of the ECU but it might be worthwhile making Bibendum sit in the back, just to see if the problem goes away. If it does, sounds like there's some sort of intermittent joint either in the ECU itself, or, more likely, in the loom that connects directly to it.

If it doesn't, I'd try changing the MAF sensor, or at the very least getting the dealer to check its function with a Select Monitor while you are driving around. Bad MAFs can, for reasons not quite understood, cause the code 22 knock sensor error on the 99-00 ECUs.

 

ok guys thanks for all of your advice i think i will take it back to the Subaru and get them to check my ecu connections, hopefully they will find the problem staring them in the face. If all fails with them then i shall take it to Alan Jeffreys of plymouth to run it up on the rollers with live data to delv deeper for the fault. my mate will have to get the bus from now on lol. cheers ill let u know how i get on.

 

replying to ur question seddomyster the check engine light is not on when i check the ecu because the light stays on at different variants, sometimes it will flick on for 1 to 2 seconds and other times it could be on for up to 2 minutes. the fault always resets itself when i turn the car off for over 3 minutes. I suppose it could be a connection error within the lum to the ecu due its hesitant flickering on and off.