P2195: O2 Sensor Signal Biased/Stuck Lean (Bank 1 Sensor 1)
The upstream oxygen or air-fuel sensor on bank 1 is stuck reporting lean, so it does not react when the mixture changes.
What P2195 means
RepairPal explains that a healthy upstream oxygen sensor should fluctuate rapidly, at least several times per second, across its normal range, and that P2195 sets when the computer sees it is not doing that and is stuck lean. On engines with wideband air-fuel ratio sensors, the code means the sensor is reporting a lean mixture that does not change as the computer adds fuel. The computer runs an active test: it deliberately enriches the mixture and watches for the sensor to respond. If it stays lean, the sensor is likely failing or biased. An exhaust leak that pulls outside air past the sensor tip can cause the same reading, as can a real lean condition from a vacuum leak or low fuel pressure. KBB says you can usually drive to a shop but should fix it quickly. Shops check fuel trims, look for leaks, and test the sensor with propane or a scan tool active test before replacing it.
Common symptoms
- Check engine light on
- Decreased engine performance
- Increased fuel consumption
- Rough idle or hesitation
- May appear with P0171
Most common causes
- Failing upstream oxygen or air-fuel ratio sensor
- Exhaust leak ahead of the sensor
- Vacuum leak causing a real lean condition
- Wiring problem at the sensor
- Low fuel pressure
- Engine computer software issue
What to check yourself first
Check for exhaust leaks at the exhaust manifold, especially a ticking sound on cold start. Inspect vacuum hoses. If fuel trims are very high, the engine may truly be lean.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace oxygen sensor | $440-$523 | RepairPal lists oxygen sensor replacement as the common repair. |
| Smoke test for vacuum or exhaust leaks | $61-$90 | Smoke testing finds vacuum and exhaust leaks that cause lean readings. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For wiring or heater circuit faults. |
| Fuel pressure test | $60-$88 | If fuel delivery is suspected. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0171 System Too Lean (Bank 1)
- P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
- P2187 System Too Lean at Idle (Bank 1)
- P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
- P2A00 O2 Sensor Circuit Range/Performance (Bank 1 Sensor 1)