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Common codes
P0420P0300P0171P0455P0442P0128P0401P0113

P0171: System too lean (Bank 1)

Drive carefully. Get it checked within a week or two.

Can I drive with P0171?

Yes, but drive carefully and get it checked soon. The engine is sucking in unmetered air or not getting enough fuel, causing hesitation and rough idle.

What does P0171 mean?

P0171 stands for System Too Lean (Bank 1).

Symptoms you may notice

  • Rough or vibrating idle when stopped in gear
  • Hesitation or mild sputtering during initial acceleration
  • Whistling or hissing noise from an intake vacuum leak

How much does it cost to fix?

Repair costs for code P0171 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:

  • Vacuum leak (cracked PCV hose or intake boot)
    $20-$100 common
  • Dirty or contaminated Mass Airflow (MAF) sensor
    $15-$40 common
  • Weak fuel pump or clogged fuel filter
    $120-$400 possible
  • Leaking intake manifold gasket
    $150-$350 possible
  • Clogged or dirty fuel injectors
    $100-$300 rare

What to do next

  1. Check all rubber vacuum hoses and the PCV tube for splits or loose connections.
  2. Spray MAF sensor with dedicated mass airflow cleaner.
  3. Inspect intake manifold gasket area with a smoke machine or soapy water spray.
Last updated: October 2026

Related codes

P0174 P0101 P0300 P0420
General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.

About this code

Code P0171 is one of the most frequent trouble codes worldwide. It indicates the computer has added the maximum amount of extra fuel (usually +25% fuel trim) and the exhaust still detects excess oxygen. While the vehicle can be driven short trips, driving long-term with a lean condition causes high combustion temperatures that can burn valves or damage the catalytic converter. Fixing simple vacuum hoses often cures it for under $30.