Fix code P0031 or P0037 Nissan Altima
If you have a P0031 or P0037 code on a Nissan Altima, you’re looking at a sensor heater problem. Oxygen sensors work when they at full operating temperature. To speed up the heating process, Nissan adds a pulse modulated heater. The ECM pulses power to the heater based on engine speed. Due to low exhaust flow at low RPMs, the ECM dictates almost 100% duty cycle power to the heater. As RPMS increase and exhaust flow keeps the sensor heated, the ECM cuts back on the duty cycle. The ECM completely turns off power to the heaters at engine speeds above 3,600 RPM.
Fuse 15 (15A) supplies power to the sensor on the red/yellow wire. Check for 12volts on that wire with engine running. If you’re getting 12 volts to the heater, check for good ground on the black wire. The ground is pulsed by the PCM. If you find no ground at the sensor, follow it back to the ECM and test there. If the ECM isn’t providing ground, you may have to replace the PCM.
If the oxygen sensor is receiving 12 volts and ground, then the heater in the sensor is bad.
©, 2015 Rick MuscoplatPosted on by Rick Muscoplat