Symptoms of P0071
- Check-engine light on, sometimes with rough or uneven running.
- Hesitation, surging, or a noticeable change in fuel economy.
- Occasionally hard starting or a smell of unburnt fuel.
Common causes of P0071
- A failing or contaminated sensor (MAF, MAP, oxygen or air-fuel sensor).
- Intake or vacuum leaks, or an exhaust leak near an upstream sensor.
- Wiring, connector, or fuel-delivery problems that skew the reading.
Useful checks before replacing parts
- Compare ambient temperature with actual outside temperature, intake air temperature, vehicle speed, heat soak, and cold-soak readings.
- Inspect sensor placement, blocked airflow, front bumper or grille damage, connector corrosion, wiring resistance, and nearby heat sources.
- Check whether the fault appears after parking hot, driving in rain, front-end repair, or rapid temperature changes.
Related OBD-II codes
These nearby fuel / air entries can help compare wording and pin down the fault area.