P0171 on a 2017 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 2017 Chevrolet Silverado 1500

Ranked from 832 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Active Fuel Management (AFM) / Dynamic Fuel Management (DFM) Lifter Failure
High severity
The AFM/DOD system is prone to lifter collapse, which can damage the camshaft and cause misfires, rough running, and engine failure. Look for ticking noises, misfire codes, and bent pushrods.
Reported in 14 NHTSA complaints
2
Vacuum Leak (Intake Manifold Gasket or Hoses)
Medium severity
Unmetered air entering the engine causes a lean condition. Inspect intake manifold gaskets, PCV hoses, and vacuum lines for cracks or leaks.
Common cause
3
Faulty Mass Air Flow (MAF) Sensor
Low severity
A dirty or failing MAF sensor incorrectly measures incoming air, leading the ECM to under-fuel the engine. Check MAF sensor readings and clean or replace if necessary.
Common cause
4
Low Fuel Pressure (Failing Fuel Pump or Clogged Filter)
Medium severity
Insufficient fuel delivery causes a lean mixture. Verify fuel pressure at the rail is within specification under load.
Common cause
5
Clogged or Failing Fuel Injectors
Medium severity
Restricted injectors fail to deliver the commanded amount of fuel. Perform an injector balance test or check for localized lean conditions.
Common cause
6
Faulty Oxygen (O2) Sensor (Upstream)
Low severity
A degraded or slow-responding upstream O2 sensor can falsely report a lean condition or fail to correct one. Monitor O2 sensor voltage switching.
Common cause
7
Exhaust Leak Before the Upstream O2 Sensor
Medium severity
Air entering the exhaust stream before the O2 sensor skews the reading lean. Inspect exhaust manifolds and flanges for soot or leaks.
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.

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Matching symptoms

Car Runs Rough