with all the o2's those trucks have. its best to just change the pair on that bank. they are located in the exhaust pipes under the exhaust manifolds. pre cats.

check rock auto they seem to be about the cheapest for ac delco sensors. where i got the 2 for my friends 04 3500 Chevy truck with a 6.0.


if you just change one of them its a crap shoot cause it maybe the other one thats bad.