Sentra Oxygen Sensor Heater Fault

A faulty O2 sensor heater is a pretty common issue. The heater helps the sensor reach operating temperature quickly, especially during cold starts. If it's not working, the sensor won't function efficiently, hence the higher fuel consumption and the check engine light. Have you checked the wiring and the connector for the O2 sensor? A loose or corroded connection can often be the culprit. It might also be worth testing the sensor itself with a multimeter to see if the heater element is actually getting power.

Thanks for the quick reply! How exactly would I test the sensor with a multimeter? Which pins should I be checking for voltage, and what readings should I expect?

Checking with a multimeter can be tricky without the exact wiring diagram for your Sentra. But generally, you're looking for two wires that are specifically for the heater circuit. Usually, they are the same colour. With the engine running, you should see around 12V across those two wires. If you don't, then the problem is likely in the wiring harness or the ECU isn't sending power. Honestly, given the potential complexity, if you're not super comfortable with electrical testing, it might be best to take it to a workshop. A faulty sensor is also a possible root cause. The repair should be around 95€, they said.

Thanks a lot! I appreciate the detailed explanation and advice. Based on what you've said, I'll probably just bring it in to a workshop, to be honest. I just don't want to damage anything.