hyundai 2000 accent.im buying a part on friday.its a oxygen sensor i got
the engine code po422.main catalyst effeiency blew threshold (bank1).my
question is do i buy the top o2 sensor or the bottom o2 sensor??first
time replaceing o2 senser.do you have to disconncet battries?to replace o2
senser? thank you

 

If you received a code p0422, it's more likely you have a catalytic
converter problem.

You should replace any oxygen sensor that's having a problem. You won't
need to disconnect the battery, just have the car off. You unplug the
sensor, and unscrew it from the manifold or exhaust pipe, depending on the
sensor being replaced.