O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
What it means
The upstream oxygen sensor on bank 1 is reading a persistently low voltage (lean signal).
Symptoms
Check-engine light, slightly worse fuel economy or idle.
Common causes
Failing O2 sensor, exhaust leak near the sensor, or wiring fault.
Recommended action
Check for exhaust leaks and sensor wiring; replace the O2 sensor if it is slow or stuck.
Related codes
FAQ — P0131
What does code P0131 mean?
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1). The upstream oxygen sensor on bank 1 is reading a persistently low voltage (lean signal).
What are the symptoms of P0131?
Check-engine light, slightly worse fuel economy or idle.
What causes P0131?
Failing O2 sensor, exhaust leak near the sensor, or wiring fault.
What should I do about P0131?
Check for exhaust leaks and sensor wiring; replace the O2 sensor if it is slow or stuck.
General reference based on the SAE J2012 standard. Exact causes for your vehicle may differ — when in doubt, consult a workshop.
← All OBD-II codes