The Quick Answer above is the generic definition. What follows is what is documented for the Volkswagen models that log P0171, checked against manufacturer data and owner reports.
DTC/P0171·Volkswagen
P0171 on Volkswagen: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Volkswagen
P0171 on a Volkswagen means the air-fuel mixture on Bank 1 (the cylinder bank with cylinder 1) is too lean: too much air or too little fuel. The ECU keeps adding fuel to hit the 14.7:1 target ratio, but it has run out of room to compensate, so long-term fuel trim climbs past about +15% and the light comes on. The single most common cause is unmetered air entering after the airflow sensor, usually a vacuum or intake leak. Most fixes land between 100 and 350 EUR.
Repair cost on Volkswagen€30 - €700
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Volkswagen Golf
2005-2024The PCV valve, also called the crankcase breather or oil separator, is the most common P0171 trigger on the Golf. On the EA888 engine the diaphragm cracks and creates a large vacuum leak, and VW revised the design several times. On TSI and TFSI turbo models also inspect the charge pipe for cracks, since boost leaks there read as lean.
What causes P0171 on a Volkswagen?
Beyond the generic causes listed on the main P0171 page, these are the documented Volkswagen-specific patterns:
Volkswagen GolfPCV and oil separator diaphragm failure on the EA888, extremely common
Volkswagen GolfCharge pipe cracking on TSI and TFSI turbo models
How to diagnose P0171 on a Volkswagen with OBD2
Follow these steps to pinpoint the root cause of P0171:
- Read short-term and long-term fuel trims with a scan tool. Long-term fuel trim above roughly +15% at idle confirms the lean condition, and if it improves at higher RPM the leak is unmetered air at idle
- Smoke-test the intake, or spray brake cleaner or carb cleaner around the intake manifold gasket, vacuum hoses, and PCV connections. A momentary RPM change pinpoints the leak
- Inspect and clean the MAF sensor with dedicated MAF cleaner, never touching the sensor element, then recheck fuel trims
- Check fuel pressure at the rail with a gauge and compare to the manufacturer specification, watching for pressure drop under load that points to a weak pump or clogged filter
- Inspect the PCV valve, oil separator, and their hoses for cracks, splits, or disconnection
- Check for an exhaust leak just before the upstream O2 sensor, which can fool the sensor into a false lean reading
- Compare Bank 1 and Bank 2 trims on V engines. If both banks read lean, suspect a shared cause such as the MAF, fuel supply, or a leak before the throttle body
How much does P0171 cost to fix on a Volkswagen? (EUR)
Estimated repair costs for P0171 in EUR, compiled across makes. Expect Volkswagen parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0171 on Volkswagen
These codes commonly cluster with P0171 on Volkswagen vehicles:
Looking for the full P0171 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0171 guideSkanyx · Volkswagen
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