P0420 & P0430

[ZedsDeadbabyZedzdead]

Hi
My E86 SI with 94k on the clock throws up these 2 codes if I drive my car for over an hour, which for me is very rare as I mostly do short journeys, I have the car booked into a local garage tomorrow but I’m really not sure what exactly I’m dealing with here, I understand the codes relate to the cat efficiency being below the thresholds on both banks but really where do I ask them to be investigate .
Does anyone have any knowledge or expertise with these 2 codes and ideally a fix please?

[Mike6]

With fault codes I would always start by clearing them and see if they come back again before taking action. I filled up with E10 the other week and after a drive I threw up oxygen sensor codes. I cleared them and they havent come back yet which makes me wonder whether initially the car was reacting to the new fuel type.

[ZedsDeadbabyZedzdead]

Hmm that’s a thinker thanks
quote=Mike6 post_id=1876748 time=1634577859 user_id=20096]
With fault codes I would always start by clearing them and see if they come back again before taking action. I filled up with E10 the other week and after a drive I threw up oxygen sensor codes. I cleared them and they havent come back yet which makes me wonder whether initially the car was reacting to the new fuel type.
[/quote]

[Jfgoldfish]

which for me is very rare as I mostly do short journeys

I think this might be the culprit. Lots of shorts journeys are a nightmare for catalytic converters.
The limits for cat efficiency on these cars is quite tight. Lots of short journeys or gently driving will often trigger these codes.
Reset and see if they return. Give it some beans often and get some miles on it!