P0171 Fault Code on Audi A3 — UK Guide (2003–2020)

P0171 on the Audi A3 — what you need to know

Audi A3 P0171 lean fault on the TFSI petrol engines is commonly caused by a faulty PCV (crankcase ventilation) system or vacuum leak. The 1.8 TFSI is well known for PCV hose failures causing lean codes.

The affected engine variants are: 1.4 TFSI, 1.8 TFSI, 2.0 TFSI. If your Audi A3 is showing fault code P0171, use our AI Diagnostic Report for a full UK-specific analysis including the exact repair costs for your engine and year.

Common causes on the Audi A3

While P0171 can have several root causes, the most common reasons this code appears on the Audi A3 in UK conditions are related to the specific engine management and emissions systems fitted to this vehicle. Always scan for related fault codes before replacing any parts — a secondary code can point directly to the root cause and save hundreds of pounds.

For the complete diagnosis guide including step-by-step testing procedures, see our main P0171 fault code page.

UK repair costs for P0171 on the Audi A3

Typical UK repair costs for P0171 on the Audi A3 range from £50 to £350 depending on the exact cause, your engine variant and whether you use an independent garage or a main dealer. Independent garages are typically 30–50% cheaper than franchised dealers for this type of repair.

Always get at least two quotes. Use our AI Diagnostic Report to understand the most likely cause for your specific Audi A3 before spending anything at a garage.

P0171 MOT implications for the Audi A3

An active P0171 fault code on your Audi A3 is likely to cause an MOT failure. Under DVSA testing standards, an illuminated check engine light is an automatic MOT failure regardless of how the vehicle drives. You must resolve this fault before your MOT test. Read our full MOT guide for more information.