This comes up quite often, I was wondering if someone could make it a sticky. If anyone has anything to add please post below and I will edit the original post.

17705 fault - things to check

17705/P1297/004759 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)

These are in order of expense, free stuff first, expensive stuff at the end. Try and borrow known working components from someone local who owns a similar VAG 1.8T 20V car to test if replacing them fixes the problem before you spend money on new parts.

This assumes you own a fault code scanner that can read and clear codes. VAG Com would also be useful but not essential apart from some of the later steps.

- Clear the fault first, drive the car and see if it comes back, if not then it was just an old stored fault code that hadn’t been cleared.

- Check large diameter boost pipes are secure, not split, and hose clips are ok

1. Turbo to pancake pipe

2. Pancake pipe itself

3. Pancake pipe to intercooler

4. Intercooler itself

5. Intercooler to throttle body

- Check small diameter vacuum/pressure pipes are secure, not split and clips are ok

1. Y piece on rocker cover

2. Pipe down from Y piece

3. S-shaped breather under inlet manifold

4. Any other vac hoses connected to inlet manifold and valves under the plate in front of the manifold, or connected to the intake pipework downstream of the turbo

- Check valves, sensor and multiplug connections

1. Pressure sensor and multiplug on top of intercooler

2. N249 DV control valve and N112 secondary air injection control valve (if present, some people have them removed) check all hoses are secure and multiplug is connected

3. N75 wastegate control valve (check all hoses are secure and multiplug is connected)

4. Diverter valve (check all hoses are secure)

5. Check wiring to all multiplugs above is not damaged

- If you have an aftermarket diverter valve, check the spring tension is set tight enough for it not to leak under boost, or consider trying the standard DV again

CHEAP CHECKS

- VAG Com log block 032. If there is a value of more than + or – 10% in the first field (additive trim) you have a vacuum leak at idle somewhere so re-check all the vacuum hoses

- VAG Com log the pressure sensor values, if it looks like there are obviously way out values then consider replacing the actual pressure sensor

- Clean throttle body, replace gasket and perform a throttle body alignment (see guide here)

- Smoke test on boost pipework

EXPENSIVE THINGS TO TRY

- Remove or replace N249 valve and/or N112 valve

- Replace diverter valve

- Replace N75 valve

- Replace throttle body

- Get the map tweaked as it may be a software issue

It can also be a software issue, I had this code and in the end needed my map tweeked to prevent it throwing the car into limp mode.

I've added that to the list, thanks Mike

Excellent post Jamie thanks

Good info indeed. I'm dealing with this problem for about six months. Tuesday i'm going to a mechanic and hopefully he'll figure it out... A good 1.8T mechanic is hard to find here.

My car is stock.

-I've replaced the DV with a stock one a year ago (however it could be broken again), i will recheck.

-I changed N75

-I have Forge boost hoses and breather y pipe. (will also change Tuesday the S shaped hose under the inlet manifold)

-I did a boost leak test and everything was ok... I will do it again.

-I cleaned throttle body and performed tba but didn't change the gasket as it was in good condition.

What is the smoke test on boost pipework?

Also can this fault appear from SAI not working correctly?

software isssue 99.9% of the time ,you can spend money on sensors and such like cahsing the cause,and will not fix it,a good mapper should be able to srt the issue

nice one, i will be removing my throttlebody this week and cleaning as i reckon at 105,000 she will need it..

 

plus judging by the amount of stuff ive had to put right from the last owner/owners,,, i dont think somehow they were capable of doing this.!!

I had this error code and changed a load of sensors etc and turned out it was a dodgy remap that was causing it. Got the car remapped by RTech and the code has not came back and the car is running great now.

Check your pressure boost regulator valve too

Great post. I've posted recently with an occasional low boost/limp mode and this code. Replaced the DV and pipework looks good. To be honest its intermittent and the car seems to reset when I 'turn it off and on again', so I'm now leaning towards a software issue. Cars only done 70k and in good health. Don't know if the car did it before remap as I had it done soon after I got it. However the mapper did a scan to check cars health beforehand and this code did not show - coincidence?