Codes keep coming back after you've fixed it?? Step in.
 

I've had an ongoing issue with my o2 sensor circuit over the past year or so.
Because I drive my back alot I don't worry about it as much, but now that it's getting cold i've been forced to seriously get it fixed.

It all started with the getting 0901 and 1001.
So I replaced the rear o2 sensor with a brand new bosch plug and play.
Didn't clear the code.
So I replaced the front one as well, cleaned egr, iacv, and put in new spark plugs.
Didn't clear the code.
Left the battery unplugged for a day, traced wires, cleaned everything there was to clean, checked voltage on coil packs and o2 sensors.
Didn't clear the code.

Now recently it's been getting alot worse and it threw the code for the front sensor.

Finally I bit the bullet and took it to the one mechanic I trust.
But before I did I called the dealership out of curiosity just to see what they would say.
He started give me some crap about needing to plug the ECU up to Nissan datebase and getting it re-programmed and crap... or at least I thought it was crap.

Low and be hold that's what it was all of the time.
Apparently the 4th gens, inparticularly the 96 models have had some issues with the ECU and codes not going away.

So if you're having problems....
Take the ECU to your local Nissan dealership and see what they say.

Mike

I just had the same prob and had to take it to the dealer. I had a short in mywiring for my MAF and MAP sensor circuits they fixed them then idrove off the loy and the light came back on for no reason they said they had a problem with the 96 sometimes