P0171 on a 2017 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 2017 Chevrolet Malibu

Ranked from 720 NHTSA owner complaints filed for this vehicle.

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1
Vacuum Pump Failure / Shattered Vacuum Pump
High severity
The vacuum pump shatters or explodes, sending metal debris into the engine and causing severe damage (like a broken camshaft) and loss of power brakes.
Reported in 5 NHTSA complaints
2
Throttle Body / Throttle Position Sensor Failure
High severity
The throttle body position sensor fails or the throttle body accumulates ice/sludge, triggering 'Engine Power Reduced' and limp mode.
Reported in 4 NHTSA complaints
3
Accelerator Pedal Position Sensor Failure
High severity
The accelerator pedal sensor loses connection or fails, causing the vehicle to lose motive power and display 'Engine Power Reduced'.
Reported in 2 NHTSA complaints
4
PCV System / Valve Cover Failure
Medium severity
A failed PCV valve or valve cover can cause a vacuum leak, leading to a lean condition and stalling.
Reported in 2 NHTSA complaints
5
Oxygen (O2) Sensor Failure
Medium severity
A faulty oxygen sensor can incorrectly read the exhaust gases, causing stalling and lean codes.
Reported in 1 NHTSA complaint
6
Turbocharger Failure
High severity
A failing turbocharger can cause a loss of engine power and trigger 'Engine Power Reduced' warnings.
Reported in 1 NHTSA complaint
7
Vacuum Leak (Intake Manifold, Hoses)
Medium severity
Unmetered air enters the engine, causing a lean condition. Look for cracked hoses or intake manifold gasket leaks.
Common cause
8
Mass Air Flow (MAF) Sensor Failure or Dirty
Medium severity
A dirty or faulty MAF sensor under-reports the amount of air entering the engine, leading to a lean fuel mixture.
Common cause
9
Low Fuel Pressure (Failing Fuel Pump or Clogged Filter)
Medium severity
Insufficient fuel delivery causes a lean condition. Confirmed by testing fuel pressure at the rail.
Common cause
10
Clogged or Faulty Fuel Injectors
Medium severity
Restricted fuel injectors fail to spray enough fuel into the cylinders, causing a lean mixture.
Common cause
11
Exhaust Leak Before the Upstream O2 Sensor
Medium severity
An exhaust leak allows outside air to reach the O2 sensor, tricking it into reading a lean condition.
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