P0171 on a 2016 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 2016 Honda Pilot

Ranked from 1,672 NHTSA owner complaints filed for this vehicle.

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1
Failing fuel injectors causing lean cylinder imbalance (Honda TSB 20-100)
Medium severity
Two owners had dealer-confirmed injector defects producing bank-specific lean codes (P219A/P219B) and an emissions-system warning consistent with a system-too-lean condition; Honda's bulletin covers debris-related injector failure on this 3.5L V6.
Reported in 2 NHTSA complaints
Parts:fuel injector
2
Weak fuel pump / low fuel rail pressure (P0087)
Medium severity
A documented low fuel-pressure code with repeated stalling on this model reduces fuel delivery enough to lean out the mixture under load.
Reported in 1 NHTSA complaint
Parts:fuel pump
3
Vacuum or intake leak
Medium severity
Unmetered air entering after the MAF sensor leans the mixture; smoke-test intake boots, PCV hoses, and manifold gaskets.
Common cause
4
Dirty or failing MAF sensor
Low severity
An underreporting MAF sensor causes the PCM to add too little fuel; clean or test against expected grams/sec at idle and cruise.
Common cause
Parts:mass airflow sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open pulls excess unmetered air into the intake, leaning bank 1; check for a rough/high idle and PCV valve rattle.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the front O2 sensor
Medium severity
A leak before the upstream sensor draws in outside air, making the PCM see a falsely lean condition; inspect manifold gaskets and flex joints.
Common cause
7
Intake manifold gasket failure
Medium severity
A leaking manifold gasket admits unmetered air directly into the runners, causing a persistent lean trim; check with propane/smoke around the gasket seams.
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