0903 is evap canister vent control valve and 0705 is the evap control system. i already put in a new evap canister vent control valve and even replaced the charcoal canister on the back of the car. so it can't be those two. my question is would a bad cat or muffler trip this two codes? if it's a bad cat, why doesn't the faulty cat code trip? i'm using the stock original cat with stock ypipe and stock catback. i'm wondering would they be also the cause of the gas fumes smell i would get from time to time? it's especially apprarent after i filled up. it's not the usual after fill up gas smell. it's very strong, almost like there's a leak. however, i checked everywhere, but there are no leaks. any help would be great. thanks.

 

No a bad exhaust system would not cause those codes to come on. The Evap system is a independent system that deals with emissions & the fuel tank. If you have an evap control sys. code you need to take it to nissan to get the specific code not just the generic since you will only be throwing darts at the problem. You could have a clogged line or a faulty solenoid.