OBD-II code guide
P0131 Oxygen Sensor Circuit Low Voltage Bank 1 Sensor 1
P0131 means the upstream oxygen sensor voltage on bank 1 is lower than expected.
What it means
The signal may indicate a lean condition, exhaust leak, wiring problem, or sensor fault.
Common symptoms
- Check engine light
- Hesitation
- Rough idle
- Poor fuel economy
- Lean running symptoms
Likely causes
- Vacuum leak
- Exhaust leak
- Low fuel pressure
- Oxygen sensor fault
- Signal wire issue
First checks
- Inspect for vacuum and exhaust leaks.
- Review fuel trims.
- Check sensor wiring near the exhaust.
- Avoid replacing the sensor before checking lean causes.