Hello, new to the forum. Im having some issues with my 2001 Maxima. I had the P0139 and P0138 codes come up. I replaced the 2 sensors, everything was fine, drove the car about 250 miles and then the check engine light came on again, saying the same things, P0138 and P0139. I cleared the codes and drove it for about 100miles.

The light came on again, and this time is read P1446 (vent control valve). Cleared it again after that and drove another 100 miles.

The check engine light came back on and this time it gave me P1038/P0139/P1446

Im not sure what to do, does anyone have any ideas? I have to get this through emissions. The shop that was recommended to me was not helpful at all.

Thanks guys.

 

Replace your Rear B1 (by the firewall) O2 sensor; that's what P0138 and P0139 are telling you. Re. P1446, it indicates a problem with your EVAP subsystem. Possible causes are:
- EVAP canister vent control valve is bad
- EVAP control system pressure sensor and the circuit
- Blocked rubber tube to EVAP canister vent control valve
- Water separator
- EVAP canister is saturated with water.

You casn find out all this from the FSM for your car. Download it from here: http://boredmder.com/FSMs/Nissan/Maxima/ .

 

Are you sure you replaced the correct O2 sensor? Below is a drawing from "5th Gen General Information, Maintenance, and Common Issues" sticky This drawing has the codes for the O2 sensors and where they are located. The O2 sensor for the P0139 & P0139 codes is screwed into the y-pipe.