P0171 on a 2010 Chevrolet Malibu

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 2010 Chevrolet Malibu

Ranked from 1,360 NHTSA owner complaints filed for this vehicle.

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1
Weak or failing fuel pump / clogged fuel filter
High severity
The fuel pump was replaced multiple times in this batch for stalling; one owner's live scan-tool data showed short-term fuel trim swing to roughly +30% (lean) during the stall events, directly consistent with a P0171 lean condition from inadequate fuel delivery.
Reported in 4 NHTSA complaints
Parts:fuel pump fuel filter
2
Corroded or failing fuel pump relay wiring
Medium severity
One owner traced repeated stalling to a burned/shorted wire feeding the fuel pump relay in the rear fuse box — an intermittent fuel-pump power loss will present as a lean condition before it stalls the engine outright.
Reported in 1 NHTSA complaint
Parts:fuel pump relay wiring harness
3
Vacuum or intake leak
High severity
The most common cause of a P0171; unmetered air past the MAF sensor leans the mixture.
Common cause
4
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting MAF sensor under-reports incoming air, causing the PCM to under-fuel.
Common cause
Parts:mass air flow sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open admits excess unmetered air into the intake.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the O2 sensor
Low severity
A leak ahead of the sensor draws in outside air and biases the reading lean.
Common cause
7
Intake manifold gasket failure
Medium severity
A leaking manifold gasket is a common unmetered-air source on higher-mileage vehicles.
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.

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Matching symptoms

Car Runs Rough