So after having a cracked cylinder head replaced (cyl3 getting coolant in it), I have got a new code.
I am getting a P0420 "Catalytic System efficiency below threshold - Bank 1".
This is a brand new code, as it was not registering this even when I had the faulty head on the vehicle. I understand the Bank 1 is for CYL1 - 3, but find it very strange it comes up now, after the big fix.
Replacing the O2 sensors look like something I can tackle myself, but was hoping I could get some insight from other Forum members.
I understand that BMW recommends replacing all four at 80-100K miles (I am at 98+). I am looking to get the SERVICE ENGINE light OUT; still trying to recover from the $4000.00 head replacement and keep costs to a minimal now. Praying it is not a bad cat, is this a pre-cat, post-cat, or BOTH sensor replacement?
Any insights would be greatly appreciated!
Thanks for reading my post.