View Single Post
      03-16-2023, 09:42 AM   #8
GrayZ4MCoupe
New Member
8
Rep
21
Posts

Drives: E86 M Coupe
Join Date: Feb 2023
Location: Midwest

iTrader: (0)

Quote:
Originally Posted by maupineda View Post
is very clear your O2 post-cat sensors are placed before the cats, and not after, so the downstream sensors see the same gases as the upstream ones; the car's ECU interprets this as faulty cats.

you need to move the 02 sensors after the cats, this means you need to modify your cats to add the bungs and install the downstream sensors after the cats.

also, your two downstream sensors are on the same header, it should be one per bank.
Would another solution possibly be to get a tune that removes the secondary O2 sensors?
Appreciate 0