OBD-II · Engine and powertrain (P)
P2195
Oxygen sensor signal stuck lean bank 1 sensor 1
What it means
The upstream (before the catalytic converter) lambda sensor on bank 1 keeps reporting a lean mixture when the ECU expects it to change. It can be a real lean mixture or a sensor or wiring fault.
Symptoms
- engine warning light
- higher fuel consumption
- possible hesitation or uneven running
- may fail the emissions part of the roadworthiness test
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | vacuum leak (crankcase breather/PCV valve, intake hoses) |
| 02 | exhaust leak before the sensor |
| 03 | dirty or faulty MAF sensor |
| 04 | low fuel pressure |
| 05 | aged lambda sensor |
| 06 | wiring fault |
What to check, step by step
- 01Read short- and long-term fuel trims at idle and at about 2,500 rpm: high trims at idle that improve with rpm point to a vacuum leak; high trims at all speeds point to fuel delivery or the MAF
- 02Smoke-test the intake and check the crankcase breather/PCV valve (a whistle or strong suction at the oil filler cap is a clue)
- 03Compare MAF readings with OEM values; clean only if permitted by the sensor maker, otherwise replace a confirmed faulty sensor.
- 04Check fuel pressure and delivery (pump, filter)
- 05Check the sensor wiring, then substitute a known-good sensor if the mixture is correct