P0171 means the engine's air-fuel mixture is too lean on Bank 1: there's too much air or not enough fuel. The ECU detected that it cannot add enough fuel to maintain the correct 14.7:1 stoichiometric ratio, exceeding its fuel trim correction range.
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 engine's air-fuel mixture is too lean on Bank 1: there's too much air or not enough fuel. The ECU detected that it cannot add enough fuel to maintain the correct 14.7:1 stoichiometric ratio, exceeding its fuel trim correction range.
Repair cost on Volkswagen€35 - €805
What does P0171 mean on a Volkswagen?
Volkswagen Golf
2005–2024The PCV valve (also called the crankcase breather or oil separator) is the most common P0171 trigger on VW Golf models. On the EA888 engine, the diaphragm cracks, creating a massive vacuum leak. VW revised the design multiple times. Also check the charge pipe for cracks on turbo models.
What causes P0171 on a Volkswagen?
Beyond the generic causes listed on the main P0171 page, these are the Volkswagen-specific patterns we see most often:
Volkswagen GolfPCV/oil separator diaphragm failure on EA888 (extremely common)
Volkswagen GolfCharge pipe cracking on TSI/TFSI turbo models
How to diagnose P0171 on a Volkswagen with OBD2
Follow these steps to pinpoint the root cause of P0171:
- Check short-term and long-term fuel trims with a scan tool. LTFT above +15% confirms a lean condition
- Perform a smoke test or spray brake cleaner around intake manifold gaskets and vacuum hoses. RPM change indicates a leak
- Inspect and clean the MAF sensor with dedicated MAF cleaner spray (do not touch the sensor element)
- Check fuel pressure at the rail with a gauge. Compare to manufacturer specification
- Inspect PCV valve and hoses for cracks or disconnection
- Check for exhaust leaks before the upstream O2 sensor that could cause false lean readings
How much does P0171 cost to fix on a Volkswagen? (EUR)
Estimated repair costs on a Volkswagen (Volkswagen parts and labour typically run 15% above the average for this code).
Prices estimated as of May 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:
FAQ: P0171 on Volkswagen
What does 'system too lean' actually mean?
It means the air-fuel mixture entering your engine has too much air relative to fuel. The ideal ratio is 14.7 parts air to 1 part fuel. When the ECU can't compensate by adding more fuel (fuel trim maxes out), it triggers P0171.
Can I drive with P0171?
For short distances, yes. But lean conditions cause higher combustion temperatures, which can damage valves, pistons, and the catalytic converter over time. Aim to diagnose and fix within a week.
Why do P0171 and P0174 appear together?
P0171 is Bank 1 lean, P0174 is Bank 2 lean. When both appear simultaneously, the cause is typically something that affects the entire engine, such as a dirty MAF sensor, weak fuel pump, or a large vacuum leak after the MAF sensor.
Can cleaning the MAF sensor fix P0171?
Often, yes. A dirty MAF sensor underreports airflow, causing the ECU to deliver less fuel than needed. Cleaning with dedicated MAF sensor cleaner is a free/cheap fix that resolves P0171 in roughly 30% of cases.
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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