emission light problem

[MartinR]

everytime i take the car on the motorway after cruising at 60ish for around 30 mile the emissions light comes on. the code reader says catalystic converter below threshold and something about 02 bank sensors (p0420). it only happens on the motorway has done it since i owned it??

cars a 182 recently changed both lambada sensors, not de-catted has ktec ultra cat and silenced ultra system if that helps?

any ideas:S

cheers

 

[montana]

Did you get to the bottom of this Martin?

I had the engine light pop up after a motorway run when slowing down , had the code read today (cheers Leeshez) and I also have the code P0420.

I have a milltek cat back system with cats still in place.

 

[MartinR]

Blast from the past lol, Yes mate it was a duff plug.

 

[montana]

Blast from the past lol, Yes mate it was a duff plug.

Yes it was, was doing the search on my phone yesterday. Duff spark plug?

 

[MartinR]

Old spark plugs... worst condition i have seen

 

[montana]

Old spark plugs... worst condition i have seen

Thanks , i will bear that in mind, although the previous owner has had the plugs changed within the last 1k. Its not come back on so far so fingers crossed!

 

[A4LLY]

I wouldn't worry about it to much. The same fault kept popping up in my old car. Took it to the garage as i had just had some work done to it and they said not to worry about it. Basically it would come on if it saw something it didn't like for a brief second but it was enough to bring up the light. Didn't effect the running of the car or effect the emissions test for the mot. Ended up buying a code reader of eBay and just cleared it when it came on.

 

[montana]

I wouldn't worry about it to much. The same fault kept popping up in my old car. Took it to the garage as i had just had some work done to it and they said not to worry about it. Basically it would come on if it saw something it didn't like for a brief second but it was enough to bring up the light. Didn't effect the running of the car or effect the emissions test for the mot. Ended up buying a code reader of eBay and just cleared it when it came on.

Yeah if it comes back i will buy one to turn it off. Like you I havent noticed any changes to the way it runs etc so will keep my fingers & toes crossed :approve:

 

[MartinR]

So just keep deleting the problem code and extinguishing the light?? Pointless imo.

Yep it may drive ok and pass emissions at the time of mot. But there is an underlying problem that needs sorting tbh.

It will come back and haunt you!!!

 

[A4LLY]

Tbh it could be anything. Just that in my case it wasn't, just the car being to sensitve. It was a vw so liked to throw up lights for fun. Most id been in had the emmisions light on. There was no obvious signs that it was causing problems and it went on for at least a year without finding anything wrong with it.

The fact you've said it's new plugs rules that out but are they the NGK ones? If not maybe a leak or the cat itself is breaking down. Might also be a fault with the downstream lambda sensor. Just monitor it but this fault isn't exactly the easiest one to solve. Even searching elsewhere there seems to be no quick fix to solve it.

www.obd-codes.com/p0420 for more info on it.