Random lack of power, VCDS fault codes: 17705 & 17963

[FJ0372]

Hey guys, as mentioned in the title I'm having issues with my 1.8t (2001, AUM, completely standard engine). It'll sometimes run fine (as far as I'm aware anyway, it's had this issue since I got it) but it will sometimes run as if it's just not producing the power it normally does. However, the problem isn't awful (i.e. it's not dead slow, just below what is expected of it).

Having done numerous VCDS scans over the last couple of weeks I have these two recurring fault codes:

17963 - Charge Pressure: Maximum Limit Exceeded
P1555 - 35-10 - - - Intermittent

17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
P1297 - 35-10 - - - Intermittent

One thing to note, is ever since having this car, between gear shifts it makes a rather nice hissing sound, not really like a proper dump valve noise but a hiss nonetheless, I thought this was normal for this type of car (being a turbo) but I've read a lot about how people insist it should be silent on A3s/S3s due to the recirculating valve.

The reason I really want these codes sorted is I'd like to take my car to one of the reputable tuners on here for a remap, but I want all faults resolved beforehand to get the best out of it.

Thank you in advance for all helpful replies!

 

[Nilz]

17963/P1555 - Boost Pressure Control: Upper Limit Exceeded
Possible Symptoms

Reduced power output
Limp mode

Possible Causes

Boost Pressure too High
Hoses/Pipes incorrect connected, disconnected, blocked or leaking
Charger Pressure Control defective
VNT (variable nozzle turbo): nozzles stuck
Solenoid Valve for Boost Pressure Control (N75) defective

Possible Solutions

Check Hoses/Pipes to/between Components
Check Solenoid Valve for Boost Pressure Control (N75)
Check / Clean / Replace Charge Pressure Control
Check / Clean mechanism for variable nozzles
***********************************************************************
17705/P1297/004759 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
Possible Symptoms

Malfunction Indicator Light (MIL) ON
Power Loss

Possible Causes

Leaking Hoses and/or Pipes between Components
Boost Pressure Control Valve (N249) faulty
Diverter Valve faulty
Throttle Body dirty
Vacuum leak

Possible Solutions

Check Hoses and Pipes between Components
Check / Replace Boost Pressure Control Valve (N249)
Check / Replace Diverter Valve
Check / Clean Throttle Body
Perform Throttle Body Alignment (TBA)
Check for Vacuum leak(s) including PCV system

These are the details from the Ross Tech Wiki, sounds like you could have a boost leak on the car somewhere, have a visual look and if you cant see anything, see if you can get a pressure or smoke test done to see if it can identify where the leaks are.

Where are you based??

 

[FJ0372]

Thank you Nilz, very insightful. That's a lot of possible causes though! I'm based around East London/ Essex.

 

[Nilz]

There are alot of causes there, but to be honest its worth getting it boost tested if you can as it sounds like alot of the resolutions are linked to this.