Darren74

About a month ago I had the CEL light come up (code 31) which was the front lambda sensor which I replaced with a new Denso sensor. The light was off & all was good then 3 days later I get another code which is code 0420 Catalyst System Efficiency Below Threshold (Bank 1)
I can reset the code but comes back a few days later.
Does anyone think this could be a dodgy sensor i got or now the front one is new it's detected something else. I've read numerous posts on here and elsewhere about the code. I'm not running a de-cat pipe so that's not the issue another post I read is that code has nothing to do with the front Lambda. Could anyone clear this up or is a trip back to the garage?

r1c

iTrader: (9)

If the front sensor was faulty, you have the possility of CAT failure now. Do you have access to a data logger??

P0420 is generally cat failure!!

Darren74

No I don't have access to a Data Logger, would this confirm what is wrong or at least confirm that the new Lambda sensor is working as it should & could be something else.
If it is the cat then would something like this be ok on a standard mapped car?
http://www.scoobyworld.co.uk/catalog...oducts_id=1111

JDM_Stig

iTrader: (3)

as u have mention 0420 is common if people have fitted a decat`d downpipe but as you havent you have to assume the rear sensor is actually faulty.

Darren74

Is there a way either I or someone with the correct equipment could pin point it to the rear sensor. I have heard that once you replace the first faulty sensor then it throws up the other one. So it won't just put a code up for just the rear sensor?