P0171Medium urgency

System Too Lean (Bank 1)

Fuel System · Air/Fuel Mixture

⚠️ Drive with caution — lean conditions can damage engine over time.
What this means

Bank 1 of your engine is running lean — too much air relative to fuel. The ECU is compensating at its correction limits. Common causes include vacuum leaks, a dirty mass airflow sensor, or a weak fuel pump. If left unaddressed, lean conditions accelerate wear on pistons and valves.

Likely causes
  • Vacuum leak (intake manifold gasket, hose)Most common
  • Dirty or failing MAF sensorMost common
  • Clogged fuel injectorsCommon
  • Weak fuel pump or clogged filterCommon
Estimated repair cost
MAF sensor cleaning or replace$100 – $300
Vacuum leak repair$75 – $250
Fuel pump replacement$300 – $700
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Frequently asked questions

What does P0171 mean?

Bank 1 of your engine is running lean — too much air relative to fuel. The ECU is compensating at its correction limits. Common causes include vacuum leaks, a dirty mass airflow sensor, or a weak fuel pump. If left unaddressed, lean conditions accelerate wear on pistons and valves.

Is P0171 serious?

Drive with caution — lean conditions can damage engine over time.

How much does it cost to fix P0171?

Repair costs for P0171 range from $100 – $300 depending on the root cause and your vehicle.

Can I drive with P0171?

You can drive short distances but should have it repaired within 1-2 weeks to prevent further damage.