Thread: 02 sensor problems, if you've had them plz read

My last resort was to make a new thread, but I've done about 10 different things and still can't figure this out. I bought my '97 SE-R a few months ago from a girl who told me ahead of time there was check engine light from the rear oxygen sensor. Well this was because there actually WAS NO rear sensor, I have no idea who or why she did it. Anyways, car ran well but felt slow as balls and within the first few weeks I had already installed bunch of mods including a new header and JWT ECU.

Emissions time came around and the check engine light was still showing up so I replaced the rear 02 sensor. Check engine light stayed on. I stopped at Autozone to see what they would get on their consult. They got rear 02 sensor AND front 02 sensor. So I replaced the front 02 sensor. Check engine light still on. Thinking it may have something to do with the JWT ECU, I swapped the stock ECU back in. Check engine light still on. So I just manually checked the stock ECU codes and got:

0707 Rear oxygen sensor

0901 Front oxygen sensor heater

I reset both the stock ECU and JWT ECU twice, drove around for a bit and as soon as I start the car up a second time the light comes back. Makes no sense to me. Both sensors are brand new. Anyone have any clue? I'm about to give up and take it somewhere.

NOW EVEN MORE B.S.

So I took the car somewhere and they said it was a blown fuse and to pick it up and drive it around to see if the light comes back on. Apparently they don't know that the light comes back after you reset the ECU on the 2nd start-up if the problem has not been solved. So they told me the light was gone. I get to the place and start the car, $109 later, and the light is on. Manually checked the codes, same exact bullshit, 0707 and 0901.

Then on the way home I heard a lound clunk, the battery and brake light come on, and the alternator belt is no longer turning. Called the repair shop and they said they didn't touch the alternator or anything. I'm so fed up with this OBD2 crap I'm thinking of selling it if I can't get an emissions waiver. It's cost me $200+ already because of this 02 sensor problem and now this.

Anyone interested in a white 97 200sx SE-R with 177k, JWT ECU, OBX header, custom CAI, Exedy racing clutch, 2.5" catback exhaust, Koyo Radiator, Tein coilovers, adjustable camber plates, crystal headlamps & corners, Lucino grille, and a nice stereo? After I get the alternator issue resolved of course. If I can't get the emissions waiver (in PA you have to show you spend more than $150 trying to get it to pass) then I may sell it.

Here's pics of what "fell out" of the engine bay today referencing the above post:





Photo for scale:

sounds like a bad ecu, i would invest in another ecu, if thats good for sure a possible short somewhere, possibly the harness is cut somewhere.

Thanks, but I did try 2 different ECU's. The stock one and a JWT I bought used from someone here on the forum; same result

Well I got the Pa emissions waiver sticker for my B14 today, since 3 different shops couldnt figure out why my perfectly working 02 sensors kept throwing codes. And I also spent um $300. So, whew.. stress level dropped now while driving the car, i just dont know how I can deal with this crap again come next year when this one expires

Is the ground wire hooked up on the exhaust, I think it is from the cat flange bracket to the body.

Mitch

Id look more into wiring, make sure the last owner didnt do any hacking or tapping to anything.
If you can get long enough lead wires for a multimeter, and a friend to help, you could start checking continuity b/t the plug under the car, and at the ECU connector.

Also good to check to see under your driver seat if there's any signs of wetness/puddles that were in the area of the o2 wiring/harness.