Posted a message on here a week ago about my engine light coming on, plugged it in and it threw up fault code P0420 Catalyst system efficiency below threshold, now a week later the engine warning light is back on, I take it it's the same fault so where doin go from here ? Replace the cat ? Or see if it's a sensor gone ? I rang subaru direct and it's gunna cost me £93 just for them to plug it into there kit, so that's a last resort

Cheers sam

 

have you decatted the downpipe ?

 

All I have changed is the standard back box for a prodrive one

 

You can buy your own code reader on Ebay for £20, resets the MIL too.

 

Bloke at work has one we've reset it already and it's come back

 

cant you borrow ,or buy a cheap replacement s/h cat and pipe inc oxy sensor see if it cures your problem


maybe the change in backpressure since fitting new backbox has fubarred the cat or sensor ???

 

I'm new to the scooby scene so have not got a clue where to find one... The car it's self Is running fine just the engine light is annoying

 

Backbox change is unlikely to throw up Cat fault codes.

If it runs fine, then Cat is probably ok. Check out the rear O2 sensor.....

 

cat effieceny is normaly what it says on the tin,backbox wont make any difference at all. what inless the cat has collapsed you wont feel any difference driving the car and chances are the 02 sensors are ok hence the fault codes. ur best bet is to get the car on a ramp, normaly if the cat has fell appart or started to you can hear them vibrate in the exhaust when u bang it with your hand. i decated my downpipe and before i got it remaped to clear the code forever if i sat at a steady 60mph for a couple of mins without fail i would get cat efficency code come up but mine was due to it sitting on a shelf at home in the garage.

 

Have had exactly the same, light came on with cat below threshold warning code.

Dealer had had a look at it on 3 occaisons now, done select monitor, emissions tests etc, all fine. Each time reset the light and it was a good few weeks before it came back on. It did however co-incide wiht a relatively long motorway journey, and also putting in a certain brand of fuel (at first we thought it may have been a bad batch)

3rd time the took it for a long run and recorded the data at a constant speed of 50 mph, as advise to do by the guys back at Subaru UK.

Apparently this has shown that the O2 sensor and AFR readings were very erratic whcih MAY be a sign that the CAT is on it's way out.

However, as said before everything is running ok and emissions are spot on (just passed MOT today )

Advise from dealer was to just monitor it and see if it comes back and starts to become more frequent in which case may have to replace the cat but otherwise not to worry as it's not causing any problems.

Would suggest you get it checked out once just to make sure everrything is ok, emissions etc and then get a reader off ebay to reset it if it comes back.

Rich