P0138 - Heated Oxygen Sensor 2 Circuit High Voltage (Bank 1)
P0139 - Heated Oxygen Sensor 2 Circuit Slow Response (Bank 1)

Those are the codes my car has been throwing the light for. Now I looked at my Maxima and it only has three sensors, not showing the Bank 1 Sensor 2. So which one would it be? Mine is federal spec, not California spec.

 

Here's the sticky on o2 sensors http://forums.maxima.org/5th-generat...bs-inside.html

 

Again like I said in my post, I do not have the California spec. Mine is federal with only three O2 sensors instead of 4. I already have the picture sheet for mine, but what's weird is it's throwing a P0138 and P0139 for bank 1 sensor 2 on the ECU machine at Auto Zone, which mine does not have.

 

I am in the same boat. My car is a federal spec and I am getting a P0138 code. Any clues by anyone? Thanks.