Hi there,

Trying to help a friend pass smog in CA. She has a 2009 R55 clubman non turbo base model. She is throwing a p0420 and the car drives like a clogged cat. Anyone got a used one they can send? I am in Santa Cruz.


Thanks!

Looks like this--

 

Also does anyone have the upstream o2 sensor for this? I think it is a wideband a/f sensor

 

i do believe that p0420 is for the downstream 02. Have you tried replacing it first before replacing the cat? i was getting this code from time to time, havent seen it since switching to national brand, shell, bp, etc, 93 octane. If the code pops back up im going to replace bottom O2 sensors first.

 

That just isn't true. p0420 is catalyst efficiency which is detected by downstream 02 yes. But there are separate codes for that if it is bad. Also downstream 02 doesn't affect A/F mixture as far as I know and the car drives like it has a clogged cat.

 

Ok, before you go blasting someone that has been on this forum for more than the 8 post you are at, how about you use that search function that we have here. You will see that code gets thrown due to the secondary O2 sensor not reading right, typical thrown with aftermarket down pipes. I was simply trying to help you find a cheaper part or you could trying clean that O2 sensor. The ecu is pulling power b/c of the code and that could be why it feels like it’s clogged.

https://www.northamericanmotoring.co...0420-code.html

https://www.northamericanmotoring.co...ode-p0420.html

 

I understand. Do you have the FSM for these cars? Or a diagnositc tree Mini recommends for a p0420 code? that would be super helpful