P0171 on a Volkswagen: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

A Volkswagen with P0171 is drivable short-term, but a lean mixture can cause misfires and should be fixed soon.

What P0171 means on a Volkswagen

On a Volkswagen, P0171 means bank 1 is running lean — too much air or not enough fuel — and the ECU has maxed out its fuel correction. VW's computer watches the MAF sensor, oxygen sensors, and fuel trims, and a lean mixture past the limit sets P0171.

Is P0171 common on Volkswagens?

P0171 is common on Golfs, Jettas, Passats, and Tiguans, especially the 2.0T. A torn PCV diaphragm is a well-known VW lean cause, along with vacuum leaks and a dirty MAF sensor.

Commonly reported on: Golf, Jetta, Passat, Tiguan.

Symptoms

Check engine light on
Rough idle
Hesitation under acceleration
Worse fuel economy

Common causes

most common: Failed PCV diaphragm (2.0T engines)
common: Vacuum leak (intake boot, hoses)
common: Dirty or failing MAF sensor
less common: Weak fuel pump or clogged fuel filter

How to fix it

Fix	DIY?	Typical cost
Replace the PCV valve or diaphragm	Yes	$50–200
Inspect and repair vacuum leaks	Yes	$10–150
Clean the MAF sensor with MAF cleaner	Yes	$10–20
Replace a weak fuel pump or clogged fuel filter	Mechanic	$300–800