Trouble code
P0131
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
What P0131 means
The upstream oxygen sensor is reporting a persistently low voltage, which reads as a lean exhaust.
Symptoms you may notice
- Check engine light
- Rough running
- Poor economy
Common causes, cheapest first
- Genuine lean condition from a vacuum leak
- Failed oxygen sensor
- Exhaust leak ahead of the sensor
- Wiring or connector fault
- Low fuel pressure
Before you buy anythingRule out a vacuum leak and an exhaust leak before replacing the sensor. A sensor reporting lean is often telling the truth.
What to do next
- Confirm the code with your own scan tool, or have it read free at a chain parts store.
- Decode your VIN so you know your exact engine and build date.
- Work down the causes above from cheapest to most expensive.
- Search NHTSA for a recall or service bulletin covering this symptom on your vehicle.
- Read the engine buying guide before ordering.
P0131 is a generic OBD-II code, standardized across every make and model sold in the US from 1996 onward. The meaning is the same on any vehicle; the specific part and its location are not.
Parts
Parts commonly needed for P0131
These go to Amazon. We earn a commission if you buy, at no extra cost to you — see our affiliate disclosure. Which one you actually need depends on diagnosis — read the note above first.
Confirm fitment against your VIN on the listing page before ordering. A part that matches your year and model can still be wrong for your build date or engine code.