O2/HO2 sensors (E36)
 

when replacing the catalytic converter on a 96 318ti 1.9 liter (M44) do you also have to replace both the O2/HO2 sensors? if so, must you get the HO2 sensor at BMW dealer? reason i ask is that BMW says they are both different, part #'s are different, but aftermarket stores only show 1 sensor #?! is it nessesary to replace the one on backside of cat? My chilton manual references both sensors, however they only say to replace the O2, with no reference to the HO2!
please help!!!

96' bmw 318tia w/ california package(targa top, not emissions)
72' harley shovelhead chopper
95' o.j. bronco (GUILTY!!!!!)

I think they are both called O2 sensors. One before the Cat, and one after the Cat. Two has difference length of wire. Do a google search again, and you should find two with diff. part numbers on the internet. Dealer is too expensive. You want to replace both if they are 60K miles or older, otherwise they might shorten the life of your new cat converter.

it is reccommended, but if the O2 sensors still work, theres no need to replace them..