P0171 on a 2019 Honda Cr V

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 Cr V

Ranked from 1,063 NHTSA owner complaints filed for this vehicle.

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1
Failed/Leaking Fuel Injectors
High severity
Fuel injectors leak or fail, causing a rich condition (P0172) or lean condition (P0171) and misfires. Confirmed by failing an A/F test, fuel intrusion in oil, and multiple warning lights illuminating.
Reported in 9 NHTSA complaints
2
Blown Head Gasket
High severity
Head gasket failure causes coolant and oil mixing, overheating, and poor combustion which can trigger mixture codes. Confirmed by compression tests, overheating, and visual inspection of the gasket.
Reported in 7 NHTSA complaints
3
Oil Dilution (Fuel in Oil)
High severity
Fuel leaking past rings or from injectors dilutes the engine oil, causing rich/lean codes, engine sludge, and potential turbo/engine failure. Confirmed by checking oil level/smell and debris in oil.
Reported in 4 NHTSA complaints
4
Vacuum Leak (Intake Manifold, Hoses, PCV)
Medium severity
Unmetered air enters the engine, causing a lean condition. Confirmed by smoke testing the intake system or listening for hissing noises.
Common cause
5
Faulty Mass Air Flow (MAF) Sensor
Medium severity
A dirty or failing MAF sensor incorrectly measures incoming air, leading the ECM to under-fuel the engine. Confirmed by checking MAF data on a scan tool or cleaning the sensor.
Common cause
6
Low Fuel Pressure (Failing Fuel Pump or Filter)
Medium severity
Inadequate fuel delivery causes a lean condition under load. Confirmed by testing fuel pressure with a mechanical gauge.
Common cause
7
Exhaust Leak Before O2 Sensor
Medium severity
Air entering the exhaust stream before the primary O2 sensor tricks it into reading lean. Confirmed by inspecting the exhaust manifold and downpipe for soot or leaks.
Common cause
8
Faulty Oxygen (O2) or Air/Fuel (A/F) Sensor
Medium severity
A degraded upstream sensor provides false lean readings to the ECM. Confirmed by monitoring sensor voltage response and fuel trims on a scan tool.
Common cause

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