Okay, in the process of battling with my service engine light, I finally decided to take my car in to a dealer and have a master Nissan Tech diagnosted my car. It took almost an hour becuase he had to run my car for like 10 mins at 2500 RPM range.

So my questions are: What's the difference between this kind of diagnosis and just reading code off the scan tool? and this time the code is different than my last one, which one should I trust? last time, it was the 02 sensor (bank 1) and this time he said it's the Cat? and he showed me all the graphs he printed out and my car never went into "safe"/limp mode..so that was a relief(btw, mode 5 is a safe mode for maximas??)and mentioned about my O2s are okay???

and how often does Random Tech high flow cat go bad like in half year? He said it's my random Cat, but i told me it's only been on the car for less than 6 months??and when i first put it on, it never gave me any error code. Now it comes to air and fuel mixture problem, since i have CAI, Y-Pipe, etc it make the ECU adjusts the fuel curves, in another words, it put more fuel than stock intake. He said that could have destroyed the Cat due to richer mixture! Oh plus the temperature outside is like 33F according to ECU

So, what should I do now? put back the stock one or get another new Random High Flow Cat, or is something else???
BTW that error code p0420, it only applies to Cali emission cars, so he did not try to re-flash my ECU

Thanks

 

help

 

i had same stuff happening, tho i don't have all those mods. take the car back and have them reprogram the ecu with their new updated catalytic parameters. the factory programming was too narrow and didn't allow for a great enough variance. once they reprogrammed my ecu, ~1 hour, no more problems.

 

I guess you didn't read my last part, the TSB regarding re-flashing the ECU for Cat is only for Cali Spec emission cars..mine is Fed emission.

 

wait... if you have fed spec, then you havea O2 sensor behind the main cat. A bad cat will trigger a light. If you have cali-spec, then a bad cat will not trigger anything since you have no sensors behind the main cat.

 

I am Fed Emission, but the first diagnosis was the Bank 1 O2 was reading lazy..now it's the Cat, that confused me!!!!

That's why I asked how often does Random Cat go bad in like half a year????

Do they have leaking issues?

 

http://forums.maxima.org/showthread.php?threadid=95398

I don't think the CAT is bad, I BELIEVE that the better flowing is causing the reading to throw the code and turn the check engine light on.

 

BTW, when you installed your RT Cat, did you make the heat shield(on RT Cat) to face up or down????

Thanks