P017100 – System Too Lean (Bank 1) – TSI / TFSI (VAG 1.8 / 2.0 TSI EA888 Gen 2 & Gen 3)
On VAG vehicles, fault code P017100 (OBD2: P0171) means "System Too Lean (Bank 1) – TSI / TFSI". It is common on 1.8 / 2.0 TSI EA888 Gen 2 & Gen 3, 1.4 TSI EA111 / EA211, 2.0 TFSI EA113 engines. Below are the real-world causes, step-by-step tests and OEM part numbers.
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P017100 quick summary
| Fault code | P017100 |
|---|---|
| OBD2 code | P0171 |
| Meaning | System Too Lean (Bank 1) – TSI / TFSI |
| System | Powertrain (Engine & Transmission) |
| Vehicles | VAG (VW, Audi, Škoda, Seat) |
| Common on | 1.8 / 2.0 TSI EA888 Gen 2 & Gen 3, 1.4 TSI EA111 / EA211, 2.0 TFSI EA113 |
| Severity | Medium |
| Can I drive? | Yes, for a short time. A lean engine runs hotter and can misfire – have it checked soon. |
| Repair cost | €20 – €400 |
Symptoms of P017100
- Rough or hunting idle
- Whistling or hissing noise from the engine bay
- Strong suction when the oil filler cap is opened at idle
- Hesitation, sometimes misfire codes
- Check Engine light
Most common causes of P017100 (most likely first)
Mechanic's Pro Tip
On EA888 engines the most common cause of P0171 is a torn diaphragm in the PCV valve (crankcase breather / oil separator). The typical sign is a whistle at idle and the oil filler cap being sucked down hard with the engine running. Check that first – then smoke-test the intake for leaks at the intake manifold, brake booster hose and diverter valve.
1.Torn diaphragm in the PCV valve / oil separator
Most likely2.Vacuum leak at the intake manifold, hoses or brake booster line
3.Leaking diverter valve or boost hose (turbo engines)
4.Dirty or faulty air mass meter (where fitted) or MAP sensor
5.Low fuel pressure (low-pressure pump, filter)
Step-by-step diagnostic guide
- 1
Read the fault memory in Engine (01); check long-term fuel trims – high positive values at idle that drop at higher rpm point to a vacuum leak.
- 2
With the engine idling, carefully lift the oil filler cap: strong suction indicates a failed PCV valve.
- 3
Smoke-test the intake system and check the hoses and the brake booster line.
- 4
Check the diverter valve and boost hoses on turbo engines.
- 5
If no leak is found, check the air mass / MAP sensor and the low-pressure fuel supply.
OEM part numbers & replacements
| Part | OEM number | Aftermarket brands | Est. price |
|---|---|---|---|
| PCV valve / oil separator (EA888 Gen 2)The version depends on the engine generation – check by VIN. | 06H 103 495 | Elring, Febi, URO | 30 € - 120 € |
Always confirm fitment by VIN before ordering. Links are affiliate links — we may earn a commission at no extra cost to you.
Frequently asked questions
How do I know if the PCV valve is faulty?
A whistle at idle, a rough idle and strong suction at the oil filler cap with the engine running are typical. Some versions have a test port, and a smoke test confirms it.
How much does it cost to fix P0171 on a TSI?
A vacuum hose costs a few euros. A PCV valve costs about 30–120 € for the part, typically 100–250 € fitted. A diverter valve or intake gasket is in a similar range.
Related fault codes
- P0171System Too Lean (Bank 1)
- P0171System Too Lean (Bank 1)
- P030000Random/Multiple Cylinder Misfire Detected – TSI / TFSI
- 16684Random/Multiple Cylinder Misfire Detected (Older VAG 5-Digit Code)
- 17544Long Term Fuel Trim Add. Air, Bank 1: System Too Lean
- 17705Pressure Drop Between Turbocharger and Throttle Valve
This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.