P0171 on a 2017 Chevrolet Malibu Eco

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 Chevrolet Malibu Eco

Ranked from 687 NHTSA owner complaints filed for this vehicle.

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1
Weak or failing fuel pump
High severity
Two owners had the high-pressure fuel pump fail outright -- one 'blew out' spraying fuel on the engine (part of a known 2016-2018 Malibu recall), the other melted wiring at the pump -- both causing reduced fuel delivery consistent with a lean condition.
Reported in 2 NHTSA complaints
Parts:fuel pump
2
Faulty PCV valve/valve cover
Medium severity
A contact's stalling below 40 MPH was repeatedly worked on with PCV valve and valve cover replacement alongside oxygen sensor swaps, pointing to a crankcase-ventilation air leak affecting the mixture.
Reported in 1 NHTSA complaint
Parts:PCV valve valve cover gasket
3
Throttle body icing/sludge in cold weather (known TSB)
Medium severity
A dealer found ice and sludge accumulated on the throttle body in cold weather, contaminating oil and cutting power -- documented under a GM technical service bulletin (10228956) that can also introduce unmetered air affecting fuel trim.
Reported in 1 NHTSA complaint
Parts:throttle body
4
Vacuum or intake air leak
Medium severity
A cracked intake boot or hose lets unmetered air into the manifold, richening the commanded fuel while the engine actually runs lean.
Common cause
Parts:intake boot vacuum hose
5
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting mass airflow sensor under-reports intake air, causing the PCM to under-fuel and trip a lean code.
Common cause
Parts:mass airflow sensor
6
Exhaust leak upstream of the front O2 sensor
Medium severity
A leak ahead of the sensor draws in outside air that the sensor misreads as excess oxygen, causing the PCM to lean the mixture further.
Common cause
Parts:exhaust gasket
7
Intake manifold gasket leak
Medium severity
A failed intake manifold gasket is a common unmetered-air path that produces a persistent lean bank 1 trim 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