2001 Nissan Maxima GLE, 159,000 miles. 3.0L V6. This car has been great, but over the past few years the " Check Engine" light has come on several times. The first time I was told to run a few tanks of premium fuel through the car and that worked, the light went off and it passed emissions inspection. The following year this did not work and I had a diagnostic run that stated there was a problem with the Bank 1 catalyst system (PO420). One place said it just needed an ECM reset, according to their TSB, but the Nissan dealer said no, that was not correct, there was a new TSB (NTB00-070b) that said to replace the front tube assembly and O2 sensor. I had this work done (not at Nissan) in 9/06 for $800 and a week later the light was on again. This time apparently a PO430 code indicating a Bank 2 issue. As I'd passed emissions I waited until this year to deal with it. Now I'm hearing two different stories from two different Nissan dealers (both owned by same guy). One says I need a new Bank 2 converter, and that the code indicates it is NOT an O2 sensor issue. The other states that this car really has only one converter, the others are resonators, and that if the converter was replaced in 06 it might be an O2 sensor issue. He says you cannot tell if it is cat or O2 from diagnostics, only from function test. Looking at some manuals (wish I'd done this sooner!) I think I have an idea how this is laid out, but how can two different places have completely different ideas of the problem? Apparently the June 04 TSB said repair could go either way. Reset ECM or replace front tube assembly (which appears to include cat) depending on ECM part number. Now I'm wondering if I got ripped off and ECM should have been reset, with no other work. If you could let me know definitively and objectively what might be wrong with this and best way to proceed it would be appreciated. As additional info. The car is high mileage. In poor condition. And needs about $1500 in suspension and exhaust work IN ADDITION to the above (which has been estimated at $750). PA has an emissions waiver I might be able to get if I spend $150 on repairs ($79 diagnostic goes toward that), which could be O2 sensor but one dealer says that isn't the problem so they can't do that repair. Car has been reliable and I really didn't want a new car payment but is it time to give up the ghost? I've made a donation so if you could respond ASAP I would appreciate it.
You say it needs other exhaust work? Would that be broken bolts at the cylinder head? If so, the o2 sensor will get false readings from the air entering the exhaust system throught the areas where they leak. Usually the head pipes have pre-cats in them, if there are TSb's pertaining to the cats, it could very welll need them, especially if the code for bank one went away after the head pipe was replaced.