P0171 on a 2015 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 2015 Chevrolet Malibu

Ranked from 267 NHTSA owner complaints filed for this vehicle.

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1
Low fuel pressure (failing fuel pump, clogged fuel filter, or faulty fuel pressure regulator)
High severity
If the engine does not receive enough fuel to match the incoming air, a lean condition occurs. One complaint mentions fuel pressure regulator codes alongside stalling.
Reported in 1 NHTSA complaint
2
Vacuum leak (intake manifold, PCV system, or vacuum hoses)
Medium severity
Unmetered air entering the engine after the MAF sensor causes a lean condition. This is one of the most common causes for a P0171 code.
Common cause
3
Faulty Mass Air Flow (MAF) sensor
Medium severity
A dirty or failing MAF sensor under-reports the amount of air entering the engine, causing the ECM to provide less fuel, resulting in a lean condition.
Common cause
4
Faulty oxygen (O2) sensor (Bank 1, Sensor 1)
Low severity
A degraded or failing upstream O2 sensor can falsely report a lean condition to the ECM, triggering the P0171 code.
Common cause
5
Exhaust leak before the upstream O2 sensor
Medium severity
An exhaust leak allows outside air to enter the exhaust stream, which the O2 sensor reads as a lean mixture, triggering the code.
Common cause
6
Clogged or dirty fuel injectors
Medium severity
Restricted fuel injectors will not deliver the commanded amount of fuel, leading to a lean air/fuel mixture in the affected cylinders.
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