P0171 on a 2011 Volkswagen Jetta Sportwagen

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 2011 Volkswagen Jetta Sportwagen

Ranked from 638 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Failing MAF/MAP sensor
Medium severity
One complaint on this exact vehicle documents a P0106 pressure-sensor code alongside a hesitant throttle response, consistent with the airflow/pressure sensor feeding the ECM bad data and causing a lean trim.
Reported in 1 NHTSA complaint
Parts:MAP sensor
2
Intake manifold gasket failure
Medium severity
One complaint on this vehicle describes the intake manifold being replaced as part of a string of related repairs, a classic bank-specific unmetered-air source.
Reported in 1 NHTSA complaint
Parts:intake manifold gasket
3
Weak fuel pump or contaminated fuel delivery
Medium severity
One complaint describes stalling/slow acceleration that the service department attributed to a contaminated fuel system, consistent with insufficient or inconsistent fuel delivery causing lean trim.
Reported in 1 NHTSA complaint
Parts:fuel pump fuel filter
4
Vacuum or intake air leaks
Medium severity
Unmetered air entering after the airflow sensor skews fuel trim lean; smoke-test the intake tract and vacuum hoses.
Common cause
5
Stuck-open PCV valve
Low severity
Excess unmetered crankcase air entering the intake leans the mixture, especially noticeable at idle.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the O2 sensor
Low severity
Outside air drawn in before the sensor falsely reads lean, prompting an unnecessary fuel trim correction.
Common cause

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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