OBD-II FAULT CODE
P0171
Fuel Trim too Lean (Bank 1)
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0171.
- Check Engine light
- Poor drivability or reduced fuel economy depending on fault
- Rough idle
- Hesitation
- Higher fuel trims
- Vacuum/intake leak
- Dirty or faulty MAF/MAP sensor
- Low fuel pressure
- Exhaust leak before O2 sensor
- Scan all modules and record freeze-frame data before clearing codes
- Check battery voltage and related fuses
- Check fuel trims at idle and under load
- Smoke-test intake system
- Inspect MAF/MAP data and fuel pressure
- Repair intake/vacuum leaks, clean/replace faulty sensor, correct fuel pressure or exhaust leak
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Disclaimer: Information is provided for general guidance only and may not apply to all vehicles. Always consult a qualified technician.