Hi all,
I am currently trying to figure out a way to remove this error code which is keeping the engine light on all the time (even returning being cleared by a code reader)
Code = P0420
Important details: I had the exhaust + catalyst replaced sometime last November with a custom built exhaust + sports catalyst, then shortly after I finally got to replacing the previous faulty EGR valve (which at the time was the only cause of an engine light). After the EGR valve was replaced, the old error was finally gone, but then the sensor for the catalyst clearly doesn’t look happy now.
Any ideas to solve this? I have thought possibly blanking the sensor may work, but I am very open to any suggestions 
My suspicion would be that the sports cat isn’t up to the job. Do you still have the original exhaust system that you could put back to eliminate the sports cat as the cause if nothing else?
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Sadly I don’t have the original catalyst. It was worn down and needed replacing so the original was scrapped.
Something I’ve thought to add; the exhaust manifold was not replaced, neither was the exhaust sensors. Could the problem be related to either of those two?
If you can find a garage with live readings on their code reader, would show you whats going on with the lambdas and if its the cat is at fault or sensors etc.
Okay yeah that sounds like a good idea, will have a look around to get the car tested at a garage
You can buy whats called an MIL light eliminator for certain cars which allows the sensor to sit slightly out of the exhaust gasses to stop the code flagging.
Not sure if ones available for yours.
