P0171 on a 2019 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 2019 Honda Pilot

Ranked from 871 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Fuel injector failure (Honda Service Bulletin 20-100 / warranty extension)
High severity
Multiple owners had fuel injectors diagnosed and replaced under a Honda service bulletin/extended warranty for codes including P219A/P219B (air-fuel ratio imbalance), which manifests as a lean-running condition, hesitation, and rough idle.
Reported in 6 NHTSA complaints
Parts:fuel injector fuel rail assembly
2
Fuel pump failure or weak delivery (recall 21-034 / high-pressure fuel pump)
High severity
Several owners report a recalled low-pressure fuel pump seal leak or a failing high-pressure fuel pump causing hesitation, rough starts, and reduced fuel delivery — conditions that can register as a lean fuel-trim fault.
Reported in 4 NHTSA complaints
Parts:fuel pump high pressure fuel pump
3
Vacuum or intake leak
Medium severity
A cracked intake boot, PCV hose, or brake booster line lets unmetered air in after the MAF sensor, leaning the mixture.
Common cause
4
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting mass airflow sensor under-reports intake air, so the PCM under-fuels relative to actual airflow.
Common cause
Parts:mass air flow sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open draws excess unmetered air into the intake, leaning the mixture especially at idle.
Common cause
Parts:pcv valve
6
Exhaust leak upstream of the front O2 sensor
Medium severity
A leak in the exhaust manifold or downpipe ahead of the upstream sensor draws in outside air, making the PCM read the mixture as leaner than it actually is.
Common cause
7
Intake manifold gasket leak
Medium severity
A degraded intake manifold gasket is a common unmetered-air entry point that produces a persistent lean code.
Common cause
Parts:intake manifold gasket

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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

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.

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.

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.

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.

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