P0171 on a 2013 GMC Sierra 1500

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 2013 GMC Sierra 1500

Ranked from 167 NHTSA owner complaints filed for this vehicle.

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1
Active Fuel Management (AFM) Lifter Failure
High severity
The AFM system on the 5.3L engine is prone to lifter collapse or failure, causing misfires, ticking/clattering noises, and stalling. This can lead to a lean condition (P0171) if unburned oxygen enters the exhaust due to a dead cylinder.
Reported in 5 NHTSA complaints
2
Excessive Oil Consumption / Piston Ring Failure
High severity
Worn piston rings or PCV issues can cause excessive oil consumption, fouling spark plugs and causing misfires that dump unburned oxygen into the exhaust, triggering a lean code.
Reported in 2 NHTSA complaints
3
Vacuum Leaks (Intake Manifold Gaskets or Hoses)
Medium severity
Unmetered air entering the engine after the MAF sensor causes a lean condition. Look for cracked vacuum hoses, a loose PCV hose, or leaking intake manifold gaskets.
Common cause
4
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 PCM to inject less fuel, resulting in a lean code. Check MAF g/s readings on a scan tool.
Common cause
5
Low Fuel Pressure (Failing Fuel Pump or Clogged Filter)
Medium severity
If the fuel pump is weak or the filter is clogged, the engine won't receive enough fuel to match the incoming air, triggering a lean code. Verify fuel pressure with a mechanical gauge.
Common cause
6
Faulty Upstream Oxygen (O2) Sensor
Low severity
A degraded or biased upstream O2 sensor can falsely report a lean condition to the PCM. Monitor O2 sensor voltage switching on a scan tool.
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