Can't Pass Inspection.... Making me crazy!!!

Ok this is whats happening.....

My 96 240sx will not pass emmision testing being that they said I have an O2 sensor code stored in my ECU. My check engine light IS working but is NOT on. The car runs great. They just said it will not pass as long as I have a code stored. I found out how to erase the code and I think I did. I went back and it failed again and when they put in their diagnostic connector this time the check engine light went on.

After much frustration this is what I figured out...........

Every time the ignition is turned on for several seconds (but not the engine) the ECU stores an O2 sensor code. Then once the car is started the check engine light comes on (with an O2 sensor code).

Now......... once I reset the ECU, the check engine light goes away and never comes back on UNTIL the Ignition is turned on (without the engine running) which then will store the O2 code.

The only way to prevent this from happening is to never turn the ignition on (without the eng running), which is fine with me BUT as you can understand everytime State emissions tries to tap into my OBDII they trip the check eng light and the O2 code again (because they have to turn on the ignition in order to do a systems check. So as you can see I am screwed.

Does anyone really think it actually could be the O2 sensor? My thinking is if it really was then why does it not go on (check eng light) when the car is running? I thought that was the job of the O2 sensor.... to monitor while the engine is running.

Has anyone had this problem before? Thanks for reading this long explanation..... I tried to be specific.

O2 can store a 'fault' yet not cause the check engine light. I'd do the O2's at a $100 bucks for the set it may save you a lot of aggravation.

My infinity J30 has a check enigne light, some times it comes on, and some times it doesn't, even when it goes off, the emissions system stores the codes if they are tripped.

just change the second 02 sensor. its nto hard. and its a small skinny little bastard. so you can take it out with a smaller wrench. its goin to be under your car after the first cat in the exhuast manifold.

The code came up for O2 but it said bay #1 so I asume that it is the first sensor at fault not the second....... right?

I want to be correct........... the first one is in the exhaust manifold and the second is in the exhaust pipe after the first cat?

Now if all the monitoring comes at the first cat then what is that second thing under my car (about mid way) that looks like a cat? Is it a cat? Is it functional?

Probably a resonator. It's like an auxillary muffler that helps muffle sound. Looks almost like a cat.

I see the resonator you are talking about.. that does look like a muffler....... what I am talking about is even before that.

This is what I see:

First: the exhaust manifold (with first O2 sensor in it)
Second: the first cat (with the 2nd O2 sensor right after it.
Third: A second cat i think (which looks like a regular cat to me)
Fourth: A resonator
Fifth: the muffler

the code says bay one so it should mean its the primary o2 sensor. cause if its the rear one it would say secondary sensor fault. also the primary is right on the exhuast manifold. then you'll see this cylinder looking thing. that is the first cat. it looks like its built into the manifold. then you will see the secondary o2 sensor.

your code should say like ho2s1(b1) the number after the s tells u if it is front or rear and the bay or bank 1 doesn't mean to much seeing as u probably have a 4 cycl.

Ok, I figured it out........ just thought I would let you all know in case it happens to you.
I got under my car and spent some time checking the whole exhaust. I felt a little exhaust leak comming from my 1st converter. I removed the first section and sure enough...... there was a small crack where the pipe meets the flange (right after the exhaust manifold). I welded the crack therefore sealing the exhaust leak. After I did that the computer did not store any more codes.
So all in all nothing was wrong with the O2 sensors even though the computer was saying there was. The tiny exhaust leak must have altered the exhaust gas content fooling the ECU in thinking there was an emmissions problem. The second thing I realized is that the Engine control system for this car is more sensitive then my girlfriend.

hey you ever want to pass emissions here some low down dirt tricks:

if you want to remove cat, goto a junkyard, get any cat... cut it in half, and the wed int onto the tail pipe, when they inspect it, emissions or police, it will look like a regular cat... but in reality is just a mask....


also pack some steel wool into the tailpipe before the sniffer... it will stop all the bad odors.. and a short fix to pass emissions in a day

you could also run the PCV from the open atmoshpere....