P0171
System Too Lean Bank 1
P0171 is an OBD-II diagnostic trouble code meaning: System Too Lean Bank 1. Common causes: air leak in the intake tract (cracks, loose connections), malfunction of mass air flow sensor or absolute pressure sensor. Estimated repair cost: $33–167.
Symptoms
- Unstable idling
- Power Loss
- Jerking when accelerating
- Increased fuel consumption
- Sometimes - the smell of hydrogen sulfide (rotten eggs)
Causes
- Air leak in the intake tract (cracks, loose connections)
- Malfunction of mass air flow sensor or absolute pressure sensor
- Dirty or faulty fuel injectors
- Low fuel pressure (pump wear, clogged filter)
- Malfunction of oxygen sensors
- Problems with the EVAP system
How to Fix
- Check the intake system for leaks (with a smoke generator or WD-40)
- Test the readings of the mass air flow sensor and oxygen sensors
- Check fuel pressure and condition of injectors
- Inspect vacuum hoses and connections
- Reset ECU adaptations after troubleshooting
Related codes
Error P0171 by Vehicle Brand
FAQ
What does the P0171 code mean?
P0171 is an OBD-II diagnostic trouble code that indicates: System Too Lean Bank 1
What causes a P0171 error code?
The most common causes of P0171 include: Air leak in the intake tract (cracks, loose connections); Malfunction of mass air flow sensor or absolute pressure sensor; Dirty or faulty fuel injectors; Low fuel pressure (pump wear, clogged filter).
How do I fix a P0171 diagnostic trouble code?
To fix P0171: Check the intake system for leaks (with a smoke generator or WD-40). Test the readings of the mass air flow sensor and oxygen sensors. Check fuel pressure and condition of injectors. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with P0171?
Limited driving only, diagnose soon
How much does it cost to fix P0171?
The estimated repair cost for P0171 is $33–167. Actual cost depends on your vehicle, location, and labor rates.
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