What's involved
What this repair actually is.
The upstream sensor sits before the catalytic converter and is the primary input the computer uses to meter fuel, so when it fails the engine runs rich or lean immediately. We replace it with a new OE-quality air-fuel or O2 sensor and verify the fuel trims return to normal.
Symptoms
How you can tell.
- Check engine light with a Bank 1/2 Sensor 1 code
- Poor gas mileage
- Hesitation or surging
- Rough idle
- Black smoke or fuel smell from the exhaust
If you delay
A failed upstream sensor makes the engine run rich, wasting fuel and slowly poisoning the catalytic converter.
Educational estimate. Real pricing depends on your vehicle, the inspection, parts availability, taxes, and shop rates. Use this as a guide while you shop quotes.