P2195 O2 Sensor Signal Biased/Stuck Lean (Bank 1, Sensor 1)

P2195 means the upstream (sensor 1) oxygen sensor on bank 1 is reporting a lean signal that will not respond normally — it stays biased lean instead of switching, so the module suspects the sensor or a genuine lean condition.

Code details

Generic OBD-II · P2

System: Fuel / Air
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the oxygen sensor before confirming the exhaust is sealed and fuel delivery is adequate, because both can drive a real lean reading the sensor is reporting correctly.

Symptoms of P2195

Check-engine light.
Hesitation, surging, or a rough idle in some cases.
Slightly worse fuel economy.

Common causes of P2195

A failed or contaminated upstream oxygen sensor.
An exhaust leak drawing air in near the sensor.
A vacuum leak or low fuel pressure.
Sensor wiring or connector faults.

Useful checks before replacing parts

Watch the sensor-1 signal live to see whether it switches or stays flat-lean.
Check for exhaust leaks and vacuum leaks near the sensor before replacing it.
Confirm fuel pressure and injector delivery are within spec.

Related OBD-II codes

These nearby fuel / air entries can help compare wording and pin down the fault area.