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P0171

P0171 on a 2020 Honda Pilot

P0171 means the engine computer is adding more fuel than normal on bank 1 because it sees too much air or not enough fuel.

Not your vehicle? See general P0171 info.

Most common causes on the 2020 Honda Pilot

Ranked from 472 NHTSA owner complaints filed for this vehicle.

Sort by:
  1. 1

    Weak or failing fuel pump (low fuel pressure)

    Medium severity

    Owners documented inconsistent/low fuel pressure and a related fuel-pump recall pattern on this model, both of which starve the engine and read lean.

    Reported in 2 NHTSA complaints
    Parts:fuel pump
  2. 2

    Failing fuel injectors

    Medium severity

    Multiple injectors failing or requiring replacement reduces delivered fuel volume, pushing the mixture lean; also flagged alongside a stuck-lean O2 sensor code on this engine.

    Reported in 2 NHTSA complaints
    Parts:fuel injector
  3. 3

    Vacuum or intake air leak

    Medium severity

    Unmetered air past the MAF is the single most common cause of a bank-1 lean code.

    Common cause
  4. 4

    Dirty or failing MAF sensor

    Medium severity

    An under-reporting MAF causes the ECU to add too little fuel for the actual air entering the engine.

    Common cause
  5. 5

    Stuck-open PCV valve

    Low severity

    Excess uncontrolled crankcase air drawn into the intake leans out the mixture, particularly at idle.

    Common cause
  6. 6

    Intake manifold gasket leak

    Medium severity

    A worn gasket lets in unmetered air downstream of the MAF, producing a steady lean bias.

    Common cause
  7. 7

    Exhaust leak upstream of the front O2 sensor

    Medium severity

    Outside air pulled in through an exhaust leak ahead of the sensor skews the reading lean.

    Common cause

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0171 on your car still needs shop confirmation before any repair.

Common symptoms

  • Check engine light
  • Rough idle
  • Hesitation
  • Surging idle
  • Poor fuel economy

What to check before replacing parts

1

Review short- and long-term fuel trims on bank 1

Look for: High positive trims (commonly worse at idle, improving with RPM) mean the computer is adding fuel to compensate for excess air or insufficient fuel — that pattern is this code's fingerprint.

2

Smoke-test the intake

Look for: Smoke escaping (or a hiss you can hear) at intake boots, gaskets, or vacuum hose connections confirms unmetered air is entering after the MAF sensor, which is the most common cause of a lean code.

3

Inspect the PCV hoses and valve

Look for: A cracked, split, or disconnected PCV hose, or a PCV valve stuck open, draws in extra unmetered air the same way a vacuum leak does.

4

Clean and test the MAF sensor

Look for: Visible dirt or oil film on the sensor element, or a grams/second reading that doesn't track expected airflow for RPM, means the MAF is under-reporting air and causing the computer to under-fuel.

5

Verify fuel pressure

Look for: Pressure below spec (weak pump, clogged filter, failing regulator) starves the engine of fuel and produces the same lean trim pattern as a vacuum leak — rule it out before chasing leaks.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Car Runs Rough