P0171 on a 2013 Chevrolet Silverado 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 Chevrolet Silverado 1500

Ranked from 364 NHTSA owner complaints filed for this vehicle.

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1
Software/Flex Fuel Virtual Sensor Calculation Error
Medium severity
The ECM incorrectly calculates a high ethanol content (e.g., 40% when running standard gas), causing it to command incorrect fueling and throw lean/rich codes. Confirmed by checking the alcohol percentage PID on a scan tool and referencing GM PIP4792D.
Reported in 1 NHTSA complaint
2
Vacuum Leaks (Intake Manifold Gaskets, Vacuum Hoses)
Medium severity
Unmetered air entering the engine leans out the air/fuel mixture. Look for cracked hoses or degraded intake gaskets, confirmed by a smoke test or spraying carb cleaner around the intake.
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 PCM to provide too little fuel. Confirmed by checking MAF g/s readings on a scan tool.
Common cause
4
Low Fuel Pressure (Failing Fuel Pump or Clogged Filter)
High severity
Inadequate fuel delivery prevents the engine from maintaining the proper air/fuel ratio. Confirmed by testing fuel pressure with a mechanical gauge at the fuel rail.
Common cause
5
Faulty Upstream Oxygen (O2) Sensor
Low severity
A degraded or biased O2 sensor can falsely report a lean condition, or fail to properly monitor the exhaust. Confirmed by observing sluggish or stuck O2 sensor voltage on a scan tool.
Common cause
6
Clogged or Dirty Fuel Injectors
Medium severity
Restricted injectors do not spray enough fuel into the cylinders, leading to a lean condition. Confirmed by performing an injector balance test or observing high positive fuel trims.
Common cause
7
Exhaust Leaks Before the O2 Sensor
Medium severity
Air entering the exhaust stream before the upstream O2 sensor tricks the sensor into reading a lean condition. Confirmed by visual inspection for soot or listening for ticking noises near the exhaust manifold.
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