Had a o2 sensor code about 500 miles ago and replaced both upstream o2 sensors. Now I have a P0138, P0139, P0440, and P0235 Any idea where I should begin?

 

P0138 & P0139 are both Rear Heated Oxygen Sensor, incorrect voltage.

The P0440 is either EVAP control system has a leak or EVAP control system does not operate properly. Possible causes are:
Incorrect fuel tank vacuum relief valve
Incorrect fuel filler cap used
Fuel filler cap remains open or fails to close.
Foreign matter caught in fuel filler cap.
Leak is in line between intake manifold and EVAP canister purge volume control valve.
Foreign matter caught in EVAP canister vent control valve.
EVAP canister or fuel tank leaks
EVAP purge line (pipe and rubber tube) leaks
EVAP purge line rubber tube bent.
Blocked or bent rubber tube to EVAP control system pressure sensor
Loose or disconnected rubber tube
EVAP canister vent control valve and the circuit
EVAP canister purge volume control valve and the circuit
EVAP canister purge control solenoid valve
EVAP canister purge control valve
Absolute pressure sensor
Tank fuel temperature sensor
MAP/BARO switch solenoid valve and the circuit
Blocked or bent rubber tube to MAP/BARO switch solenoid valve
O-ring of EVAP canister vent control valve is missing or damaged.
Water separator
EVAP canister is saturated with water.
EVAP control system pressure sensor

I don't know about the P0235 code. The info I have says it is a Turbocharger/Supercharger boost circuit A problem. I must have the wrong list or maybe the ECU is throwing a ghost code.

 

Oh ok. Thought the 2 new up streams I installed went bad. Guess I change the one in the cat this time.

 

It sounds like you don't have a FSM. Most of the codes are in the EC (Engine Control) section.

If you don't have a FSM, download it from here:

http://boredmder.com/FSMs/Nissan/Maxima/

 

i wouldnt worry about the rear sensor codes. GIve it a wk to break the new sensors in.

 

The new ones have been in almost a month

 

That should be enough time I think.Hope you get the issue sorted out

 

Me to. Going to have the rear o2 changed this weekend and have a smoke machine hooked up to see if there is any leaks in the avap syatem.

 

This maybe a silly question, but did you reset the ECU after the O2 sensor replacement and are you getting these code after the replacement?

Either your fuel pressure is messed up or you may have exhaust leak (or created exhaust leak by not installing the O2 sensors properly)

As far as I know, O2 sensors don't need break in period - they should work properly straight out of the box (if installed properly)

 

Yes reset the codes with a scanner. Had the p0440 code before the P0139, P0138 is new