Oxygen sensor signal biased or stuck lean — Bank 1 Sensor 1
The controller determined that the Bank 1 upstream feedback signal remained on the lean side or did not respond as expected.
Conditions that can produce P2195
These are diagnostic branches, not a ranked parts list. Prevalence and testing order depend on the exact vehicle and failure scene.
- Unmetered air or low fuel delivery
- Exhaust leak before the sensor
- Sensor, heater, wiring, or connector problem
- Injector or bank-specific mechanical condition
- Incorrect sensor or interpretation
What to inspect next
- Review fuel trim and bank comparison
- Identify narrowband versus wideband sensor behavior
- Check exhaust integrity and heater/circuit evidence
- Use a controlled mixture-response test from exact service information
Evidence that strengthens the answer
Verify the repair
Preserve the pre-repair record, document exactly what changed, then repeat the relevant operating condition safely. Confirm no current or pending fault returns, review permanent-code and readiness state where applicable, and state which tests or modules remained unavailable.
This page explains a commonly standardized code at a general level. Confirm the exact definition, module, status, test conditions, thresholds, wiring, and service process for the vehicle application using current official information.