P0171 on a 2021 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 2021 Honda Cr V

Ranked from 311 NHTSA owner complaints filed for this vehicle.

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1
Clogged or failing fuel injectors
Medium severity
Multiple owners of this vehicle had fuel injectors replaced for carbon buildup, drivability, and misfire issues (one directly causing spark plug damage), which can unbalance the mixture toward lean.
Reported in 3 NHTSA complaints
Parts:fuel injector
2
Failing high-pressure fuel pump
High severity
Two owners of this exact vehicle had a confirmed failed high-pressure fuel pump diagnosed after a sudden loss of power/stall event, one of which also destroyed all four spark plugs.
Reported in 2 NHTSA complaints
Parts:fuel pump
3
Vacuum or intake air leak
Medium severity
Unmetered air entering downstream of the MAF sensor leans the overall mixture; check intake boots and vacuum hoses.
Common cause
Parts:vacuum hose intake boot
4
Dirty or failing mass airflow (MAF) sensor
Medium severity
An undercounting MAF sensor causes the ECU to under-fuel across the board.
Common cause
Parts:mass airflow sensor
5
Intake manifold gasket leak
Medium severity
A leaking manifold gasket is a common lean-code source; a smoke test at idle usually finds it.
Common cause
Parts:intake manifold gasket
6
Exhaust leak upstream of the front oxygen/air-fuel sensor
Medium severity
Outside air drawn in ahead of the sensor makes the ECU read a falsely lean exhaust stream.
Common cause
Parts:exhaust manifold gasket
7
Stuck-open PCV valve
Low severity
Excess air pulled through a stuck PCV valve skews the fuel trim lean, especially at idle.
Common cause
Parts:PCV valve

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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