17705 – Pressure Drop Between Turbo and Throttle Valve

Overview

17705 fault code is a pretty common sight for most 2001+ 1.8T owners, and many often spend hours and hours chasing the fault replacing items such as MAF sensors, dump valves, MAP sensors, split pipework and boost leaks.  However, the code often appears once the outside temperature starts to drop and the mornings become colder.  This code often comes attached with limp mode which is fixed by a ignition cycle. It is more prominent on remapped cars.

The fault is triggered by a deviation between the throttle plate and dump valve, MAF and MAP sensor and air drawn in at X*c temp. The ecu code has a modelled structure of the air paths based on mathematics.  It’s the drop in modelled pressure and actual upstream pressure which causes the code.

Alternate fault codes from generic code readers: 17705/P1297/004759

17705 Diagnosis

Fault Locations:
Pressure Drop between Turbo and Throttle Valve.

Possible Causes:
Engine Management Light (EML) ON.
Power Loss/Limp Mode
Leaking boost pipework or connections.
Boost Pressure Control Valve (N249) faulty.
Dump/Recirc Valve faulty.
Throttle Body dirty.

Possible Solutions:
Look for split./loose Hoses and Pipes between Components.
Check / Replace Boost Pressure Control Valve (N249).
Clean Throttle Body.
Check / Replace Dump Valve.
Perform Throttle Body Alignment via VCDS
Software Patch via FVPDKLDUS in ECU Mapping (set to 0 across the 5×1 map)

Other Causes

If you have checked all previous boost pipework, vacuum pipes and are sure that you don’t have a boost/vacuum leak (a great way to confirm is via a Smoke Test) then one of the causes of this fault code is actually a software bug in the ECU mapping.  The majority of leading UK tuners will already have this issue patched in their remaps, however they aren’t always patched.    If the 17705 fault code is patched via FVPDKLDUS in the ECU mapping by setting the 5×1 map to 0, then genuine pressure drops from faulty pipework will still show as genuine.

Finally, we understand that not everyone will be able to patch this code themselves, however there are many tuners out there that can assist with this for a very small fee.  We just don’t want people spending £000’s and hours and hours of time chasing phantom error codes now the code mornings are happening when in reality, the issue could be a simple bug in ECU software.