17705 – Pressure Drop Between Turbocharger and Throttle Valve (VAG 1.8T 20V)
On VAG vehicles, fault code 17705 (OBD2: P1297) means "Pressure Drop Between Turbocharger and Throttle Valve". It is common on 1.8T 20V (AEB, AWT, AWM, AMB, BEX, AUQ), 2.0 TFSI (BPY), Golf IV, Passat B5, Audi A4 B5/B6, A3 8L/8P, TT 8N, Leon 1M engines. Below are the real-world causes, step-by-step tests and OEM part numbers.
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17705 quick summary
| Fault code | 17705 |
|---|---|
| OBD2 code | P1297 |
| Meaning | Pressure Drop Between Turbocharger and Throttle Valve |
| System | Powertrain (Engine & Transmission) |
| Vehicles | VAG (VW, Audi, Škoda, Seat) |
| Common on | 1.8T 20V (AEB, AWT, AWM, AMB, BEX, AUQ), 2.0 TFSI (BPY), Golf IV, Passat B5, Audi A4 B5/B6, A3 8L/8P, TT 8N, Leon 1M |
| Severity | Medium |
| Can I drive? | Yes, but power is reduced and a large boost leak makes the turbo work harder. Have it repaired soon. |
| Repair cost | €10 – €400 |
Symptoms of 17705
- Check Engine light
- Loss of power, especially at higher revs
- Hissing or whooshing under boost
- Boost not building as before
- Rough idle (if a vacuum leak is involved)
Most common causes of 17705 (most likely first)
Mechanic's Pro Tip
On 1.8T and 2.0 TFSI engines this code nearly always means a leak in the charge pipes or a torn diverter valve (N249/'DV') diaphragm. Pressure-test the intake from the turbo outlet to the throttle body and check the DV first. On the 2.0 TFSI BPY engine also check the updated crankcase breather valve – with full vacuum under the oil cap at idle it is faulty.
1.Leaking charge air hose, intercooler or pipe clamp
Most likely2.Torn or leaking diverter valve (N249 / DV)
3.Faulty boost pressure control valve (N75)
4.Vacuum leak, including the PCV / breather valve
5.Dirty throttle body
Step-by-step diagnostic guide
- 1
Read all codes and log specified vs. actual boost pressure during a full-load pull in 3rd gear.
- 2
Pressure-test the charge air system (turbo outlet to throttle body) and look for leaks at hoses, intercooler and clamps.
- 3
Check the diverter valve diaphragm and its vacuum line; check the N75 valve and hoses.
- 4
Check for vacuum leaks and the crankcase breather; clean the throttle body and run a throttle body alignment.
- 5
Repair, clear codes and confirm boost follows the specified value on a test drive.
Frequently asked questions
What is the diverter valve (DV)?
A valve that releases boost pressure when the throttle closes. Its rubber diaphragm tears with age, causing a boost leak and this code.
Can a dirty throttle body cause 17705?
Sometimes – clean it and run the throttle body alignment, but check for leaks first.
Related fault codes
- P0299Turbocharger / Supercharger 'A' Underboost Condition
- 17964Charge Pressure Control: Negative Deviation (Underboost)
- 16684Random/Multiple Cylinder Misfire Detected (Older VAG 5-Digit Code)
- 17544Long Term Fuel Trim Add. Air, Bank 1: System Too Lean
- 17748Crankshaft/Camshaft Position Sensor Signals Out of Sequence
- 17965Charge Pressure Control: Positive Deviation (Overboost)
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.