P0171 on a 2017 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 2017 Honda Cr V

Ranked from 1,740 NHTSA owner complaints filed for this vehicle.

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1
Blown Head Gasket / Coolant Leak into Cylinders
High severity
Coolant leaking into the combustion chamber causes misfires, rough running, and lean codes. Look for coolant loss without external leaks, white smoke, or combustion gases in the cooling system.
Reported in 13 NHTSA complaints
2
Faulty Fuel Injectors
Medium severity
Clogged or failing fuel injectors cause a lean condition and misfires. Look for misfire codes (P0300-P0304) alongside the lean code, and verify injector flow/spray patterns.
Reported in 7 NHTSA complaints
3
Low Fuel Pressure (Failing Fuel Pump or Filter)
Medium severity
Insufficient fuel pressure prevents enough fuel from reaching the injectors, causing a lean condition. Test fuel pressure at the rail to confirm.
Reported in 1 NHTSA complaint
4
Vacuum Leak (Intake Manifold, Hoses, PCV)
Medium severity
Unmetered air entering the engine causes a lean condition. Check for cracked hoses, loose intake manifold bolts, or a faulty PCV valve using a smoke machine or listening for hissing.
Common cause
5
Faulty Mass Air Flow (MAF) Sensor
Low severity
A dirty or failing MAF sensor under-reports the amount of air entering the engine, causing the PCM to inject too little fuel. Clean the sensor and check its data readings.
Common cause
6
Faulty Oxygen (O2) Sensor (Upstream)
Low severity
A degraded upstream O2 sensor can falsely report a lean condition, causing the code. Monitor sensor voltage switching and response time.
Common cause
7
Exhaust Leak Before the O2 Sensor
Low severity
Air entering the exhaust stream before the upstream O2 sensor tricks it into reading lean. Look for soot marks or listen for ticking noises near the exhaust manifold.
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.

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Matching symptoms

Car Runs Rough