P0420 Still

AntSSSS

Member
Hi Guys,

first post - so firslt and formost - hello :)

Ok - so my problem:

Car is a Vec 2001 2.2 150 Sri (z22se of course)

Basically - I keep getting the eml with: P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
I clear the code and then 10 - 30 or so miles later it will come back.
What has been done so far:
- When I bought the car it had a brand new exhaust from the manifold back - so new cat, mid and rear box. This was producing the code as above
- I changed the rear box for a letterbox irmy exhaust. This was still producing the code - although I didnt expect this to change
- Bearing in mind the cat was brand new - I got two brand new Genuine VX Lambda sensors and fitted them. This was still producing the code as above, no change
- Knowing that the cat was not a genuine VX one and was a aftermarket cheapy one - I got a genuine VX one (all be it second hand) which had the pre cat removed and fitted that. This was still producing the code as above, no change.
- I then fitted a EGR cheater and blank from here.. this made a big difference to pickup and idle. But still the same code as above.

So I am now at a loss.. In a nutshell I have done everything I can think of to resolve this yet still its present.

It does seem to come on after a good 'enthusastic' drive, but never straight away - it seems to be after between 10 - 30 miles of the last eml reset.

I do run it on V-Power petrol only, and have never used anything else since I got the car.

So really after some help chaps as this is getting VERY annoying and the car is so nice to drive this lets it down.. MPG seems reasonable and there are no running issues.

HELP?? :)

thanks Anthony
 

vocky

Staff
P0420 Catalyst System Low Efficiency

the ecu thinks your cat isn't working correctly, so you replaced the lambdas and cat, which would be the correct thing to do.

next job would be to check the wiring from the lambda plug back to the ecu, also might be worth replacing the coolant temp sensor
 

AntSSSS

Member
Hi Mate,

Forgot to mention that I have changed the CTS also..

Not checked the wiring I must admit as I thought if it was a wiring issue then it would be constantly present... and I seem to be able to make the light come on if I rag the car a bit.. but that may be co-incodence I suppose.

maybe it could still be wiring tho?
 

vocky

Staff
if there is a bad connection on the mixture lambda you could get over fuelling and the cat might not be able to deal with the gases notsure.gif
 

AntSSSS

Member
good thought and worth a check..

I did wonder if there may be an ECU update at all that would help in addressing this - not sure how I would find out without booking the car into VX tho thats the prob..
 
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