My car has little over 5000 miles, recently installed the apexi midpipe (no resonators) and now getting CEL with P0420 code. There are no leaks i can tell, and I doubt the CAT is bad. Is it possible that the downstream O2 sensor went bad? Already check and wires are not twisted.

And... just for me to be clear, is bank 1 @ the right side (passenger side)?

thanks for any assistance.

 

does that midpipe delete the cats? that code is usually associated with cat deletes without use of defouler/o2 sim.

if not, just clear the code and see if it comes back.

 

crush washer. get new ones.

 

Cats were not deleted. Car has less than 6k miles. I clear the cel but it return after 100 miles or so. I think the second o2 may have been damaged. I just need to know if that can cause the cel.

Thanks for your reply

 

Yeap, damaged oxy sensor can cause a P0420 code.
Since work was done in the mid pipe section, I think one of these are possible:
Damaged or faulty rear oxygen sensor(s)
Damaged oxygen sensor wiring, bad oxygen sensor connection
Leak in mid pipe exhaust, bad gasket or improper flange mating.

 

that is kind of what i was thinking. i will be checking the connection of the mid pipe again, and if good, will replace O2. hpefully that will solve it.