Hi all,

Have this car in with a "P0420 Catalytic Converter Conversion" fault.

If you reset the error it drives for a week or so fine, and then will trip the EML and log this fault. Its been to another garage and already had a new [aftermarket] catalyst and NTK post-cat O2 sensor but still the fault occurs. We've smoke-tested the intake and all is OK, smooth running values look ok.

Autologic fault reported as:

(165) A5 EUIII code p0420 Catalytic converter conversion
Currently present
Fault is not sporadic
Undetected for 48 times
IMPLAUSIBLE VALUE

Anybody come across this before and have any ideas where to look? Thanks.