Testing N75 with vag-com?

I have read through quite a few posts regarding the testing of the N75 valve. Can anyone tell me how, if it is possible in the first place, to check the functionality of the N75 with vag? I have a persistent code (17964) and all the vacuum lines seem to be in good place. My question is, how can I tell if I have a bad N75 or not? What would the part number be for a 2002 Golf Auto TDI?

A VAG-COM selective output test of the N75 will indicate its functionality. See this info: http://www.ross-tech.com/vag-com/tour/out_test.html

The N75 part number for post 99.5 models is 1J0906627A.

Thanks a lot. What am I looking for inthe test? Should the car be running?

POWERSTROKE said:

Thanks a lot. What am I looking for inthe test? Should the car be running?

Click to expand...

You should be looking at the actuator arm of the turbo for movement - 1/2 in. at least. No movement would indicate either bad N75, or bad turbo actuator, or stuck VNT mechanism inside the turbo. Yes, the engine should be running. Another way to implement the test is to go to the engine section in VAG-COM, go to measuring blocks, go to channel 11, and then choose basic mode to start the test. The N75 should switch back and forth - about 10 sec on, 10 sec off. You should hear a 'clicking' of the N75 when it switches. To double check the N75 you can detach the vac hose going to the turbo actuator and in its place hook up a short piece of vac tubing to a vac gauge. If you don't have a vac gauge you can tape a very small plastic bag tightly to the vac hose. When the N75 kicks on/off the plastic bag will show the vac suction.

If you want to check if the VNT actuator is stuck, you can use your left hand to reach down to the turbo (when its cold).
With your hand feel to the actuator rod and up to where it pivots there is this 1/2 piece coming out of the turbo. Move it down to feel how it goes to low boost mode, and see if it springs up if you let go. If its kinda "crunchy", not smooth going up and down, there is soot buildup where the vanes are.

The car starts of running you need to build up the vacumn for the tests then with the car running start the output tests you will run through a few till you hit the stop engine check valve leaving the engine off I believe there is one more test before the N75, Once you come to the N75 hit the button and listen for the n75 making a clicking sound and you may also be able to hear the VNT rod pumping up and down about 4 times till the vacumn runs out. You can also with help use gloves and put your hand down behind the engine and find the VNT rod have you helper run through the tests and feel if the rod is moving 1/2 to 3.4 in. with that code I would also be looking for any leaks in the Intercooler pipes and the vacumn lines. the intercooler rubber parts can and do split over time and the vacumn line wear out. If you have not checked you intake this may be a good time to make sure it is not clogged up.

I know this thread is ancient but it was useful to me yesterday. Turns out all I had was a stuck check valve off the N75. A little brake cleaner and car runs like new. No more CEL.

2002 ALH
I plugged in VCDS and went to the 011 measurement. Car is running.
At idle:
-Engine Speed - 903/min
-Boost specified - ON or OFF - no mbar measurement at all. It is 0 on graph
-Boost actual - ~999 mbar
-Charge Pressure - 0% or 99%

If rev it up past 1500-1600 it errors out.

Will someone help me interpret this, please?

Thanks
GF