I've been chasing the reason why I have thrown two ses codes in the last three months. I knew the y pipe was to blame but I wanted the exact reason. Finally got a definitive answer:

At first I thought that the y was blowing 02 sensors. Then thought that my catalytic converter was bad. The first light was from a bad 02. This last light was from the absence of the main precat that is found in the stock y pipe. (The big bulge). How can a y pipe be expected to not throw codes when the main precat isnt there? I have a 00 Cali spec Max. When I got my y pipe sticker on it said 01 Fed spec. It fit fine but could that be the reason. I have also heard that 00 cali's have issues with codes and y's. I love the power increase and would hate to return to stock but I think I'm gonna have to.

Anyone with similar experiences? Any feedback or help is appreciated.

 

I have cali spec and had my y-pipe on since last May and never had any codes yet.

 

SES is on all the time, code was for "cat operating below operating spec." There are no sensors after the Cat ... Don't know it would know i was having a prob with my cat (or lack there of) with my strait through exhaust with the strait pipe just thought it was not enough backpressure. Mine is cali spec too. I'm dreading emissions I need to get a cat. Again any more insite would be GREAT

 

i betting its from having a fed spec y-pipe on a cali-spec car.

 

yes there is!! its about an inch behind the cat.
i want to do the straight pipe but am worried about what will happen with that sensor.
im pretty sure it tells the ECU if the cat is working. so if the cat isnt there, the ECU will think its not working. will it throw a light? will it adjust fuel/air mixture? i dont want to lose performance

 

Is it just that the light's on or do you hear/feel something's wrong?

 

there is an o2 behind the cat on fed spec maximas but not cali spec. i have had my y pipe on my cali spec 2k1 for about 2.5 years with no related check engine lights. the reason the poster may keep blowing o2 sensors is that nissan has a tsb related to replacing and flashing the ecu. im guessing the flash is what is keeping you from keeping a lasting o2 sensor.

 

Well this SES light is supposedly not an 02 sensor, according to the dealership. They say that the light is from the lack of the major precat (again the big bulge) in the factory y pipe! I dont know who/what to belive, I just wish I had some definitive answers.

 

i never got a light for lack of the precat.
maybe thats just a cali spec problem

 

Just the light