P0171 on a 2019 Honda Accord Hybrid

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 Accord Hybrid

Ranked from 529 NHTSA owner complaints filed for this vehicle.

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1
Weak or failing fuel pump (reduced rail pressure)
High severity
Multiple owners on this VIN set describe fuel pump failures/stalling tied to Honda's fuel pump impeller recall (23V-858); insufficient pump output under load can pull the mixture lean.
Reported in 4 NHTSA complaints
Parts:fuel pump
2
Clogged or malfunctioning fuel injector(s)
Medium severity
Owners on this VIN set had injectors replaced for misfire/rough-running complaints; restricted injectors reduce delivered fuel and skew trims lean.
Reported in 2 NHTSA complaints
Parts:fuel injectors
3
Vacuum or intake air leak
Medium severity
Unmetered air entering after the MAF sensor (cracked hose, brake booster line, intake gasket) skews the fuel trim lean, especially at idle.
Common cause
4
Dirty or failing mass airflow (MAF) sensor
Medium severity
A contaminated or drifting MAF under-reports intake air, causing the PCM to under-fuel; look for a smoothed or erratic grams/sec trace on a scan tool.
Common cause
Parts:mass airflow sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open adds an unmetered air path into the intake, pushing fuel trims lean particularly at idle/cruise.
Common cause
Parts:PCV valve
6
Exhaust leak ahead of the upstream O2 sensor
Low severity
A leak before the front oxygen sensor draws in outside air, making the sensor falsely read lean and trigger fuel trim correction.
Common cause
7
Intake manifold gasket leak
Medium severity
A worn manifold gasket lets in unmetered air downstream of the throttle, most noticeable as a lean condition at idle.
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