The code means that there is a problem with the heater element circuit of the heated oxygen sensor. Water getting inside the heated oxygen sensor connector can cause the heated oxygen sensor fuse to blow, which is a very common problem for this type of code. Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors.
For Nissan models 2005 and up see: P0031 Nissan
There is a Factory Service Bulletin for the following Nissan models:
2002 Nissan Sentra
2002 Nissan Altima
2002 Nissan Sentra and Altima Factory Service Bulletin OBDII Code P0031
Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
The cost to diagnose the P0031 Nissan code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.
The P0031 is set when the ECM detects an excessively low voltage through the heated oxygen sensor heater circuit
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