a bad o2 will not cause the car to not start it may run like crap though but it will run.
when u add the wideband usually u put it where the rear on goes and then get a tune or mil eliminator to get rid of the CEL. but the rear o2 has nothing to do with car performance its just there to make sure the cat is doing its job
HATCH NATION #56
2004 Sonic Blue SVT!!! 2.5" orp and flex and trubendz catback, toms tune, steeda sts, custom intake, good ol motocraft copper plugs!