P0171 on a 2019 Honda Civic Hatch Type R

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 Civic Hatch Type R

Ranked from 420 NHTSA owner complaints filed for this vehicle.

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1
Weak/failing fuel pump (impeller defect, open recall 23V-858)
High severity
An unusually large number of owners report the recalled in-tank fuel pump impeller deforming and failing, causing stalling, delayed/weak starts, and rough running from inadequate fuel delivery -- a direct lean-condition cause.
Reported in 18 NHTSA complaints
Parts:fuel pump
2
Failing or discontinued fuel injector
Medium severity
Owners report fuel injectors failing outright (one describing it as a known, discontinued part Honda hasn't recalled) with symptoms matching the fuel-pump complaints -- a restricted or malfunctioning injector can also produce a lean condition.
Reported in 2 NHTSA complaints
Parts:fuel injector
3
Boost/turbo intake hose disconnect (vacuum leak)
Medium severity
One owner reports a hose repeatedly coming off the turbo, causing the car to lose the ability to accelerate -- a disconnected boost/intake hose admits unmetered air and leans the mixture.
Reported in 1 NHTSA complaint
4
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting MAF under-reports incoming airflow, causing the PCM to under-fuel.
Common cause
Parts:MAF sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open adds unmetered air to the intake, leaning the mixture at idle.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the O2/air-fuel sensor
Medium severity
An exhaust leak ahead of the sensor draws in outside air and skews the reading lean.
Common cause
7
Intake manifold gasket leak
Medium severity
A leaking manifold gasket admits unmetered air directly into the runners, producing 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