17964 Diagnostic Code

**fullerlee** · 27-09-2008,08:44 PM

Hello all,

I've got a problem with my 2001 Passat 130TDI.

Plenty of power down low, but around 3k RPM it drops to nothing and no apparent boost until the car is rebooted.

VAG-COM is showing a 17964 which from what I hear is fairly common.

I've checked most of the pipes from the air box, hotside of turbo, and intercooler down-pipe and found no apparent problems. VNT appears to move ok when under vacuum (as hard as I can suck, it moves noticably).

When I reassembled everything except the engine covers and the snorkus (left the bonnet cracked to get a bit of air in) and went for a spin, everything seems fine again. Loads of smooth power all the way through, motorway flooring in 5th. No problems at all, no diag codes

I refitted the snorkus and engine covers, went for another drive, and problems again as soon as I got into heavy boost. Back to code 17964.

I'm thinking the next thing to check might be the N75 - my question is whether this is a good idea, and also how to check it?

Appreciate any thoughts.

Thanks,

Lee

**Crasher** · 27-09-2008,09:21 PM

Remove the small vacuum pipe from the servo pump to servo feed hose and suck on it, you should not be able to suck air though it. If you can, you should be able to hear where the air is coming in so follow it back to trace the leak. The two favourites are near the EGR solenoid under the coolant reservoir where the plastic pipe rubs though and inside the metal clip on the air box where the plastic pipe drops down to the N75 valve. I have dome two Passat 130’s with this fault this week. I use a small length of 3-mm vac hose to fix it.

**fullerlee** · 27-09-2008,09:26 PM

Originally Posted by Crasher

Remove the small vacuum pipe from the servo pump to servo feed hose and suck on it, you should not be able to suck air though it. If you can, you should be able to hear where the air is coming in so follow it back to trace the leak. The two favourites are near the EGR solenoid under the coolant reservoir where the plastic pipe rubs though and inside the metal clip on the air box where the plastic pipe drops down to the N75 valve. I have dome two Passat 130’s with this fault this week. I use a small length of 3-mm vac hose to fix it.

Thanks for the info, will try it. Could you explain where the servo feed hose is please? Cheers

**Crasher** · 28-09-2008,02:57 PM

On the back of the head there is a dual pump called a tandem pump as one half delivers the second stage of fuel pressure and the other generates a vacuum for the brake servo, EGR valve, shut off flap and turbo vane control. This pipe (around15-mm outside diameter) comes off and runs along the bullhead for a short distance and then goes into a grommet that transfers the vacuum to the other side of the bulkhead into the plenum chamber where another pipe takes it to the servo. Just before the pipe goes into the grommet, there is a small 3-mm fabric covered vacuum hose on a bulged section (which is a non return valve) which goes to a Y piece that sends the vacuum off down to the N75 valve and in the other direction to the EGR valve control solenoid and also to the shut off flap solenoid. Pull the small hose off of the servo pipe (be gentle, or you could snap the pipe off and then need a new servo pipe) and suck on the small hose.

If you are stuck, tell me and I will take a picture of one I just finished putting a new head on yesterday as it is still on the ramp waiting for a road test tomorrow before handing it back. He will get a shock when he drives it as it came in for losing water but had no power either which he didn’t realise as he bought it like that. It is quite nice to be able to give it a major power increase for no cost as he will have some tangible benefit for the couple of thousand pounds fitting a brand new head/valves/cam/lifters etc has cost.

**fullerlee** · 28-09-2008,08:39 PM

Originally Posted by Crasher

On the back of the head there is a dual pump called a tandem pump as one half delivers the second stage of fuel pressure and the other generates a vacuum for the brake servo, EGR valve, shut off flap and turbo vane control. This pipe (around15-mm outside diameter) comes off and runs along the bullhead for a short distance and then goes into a grommet that transfers the vacuum to the other side of the bulkhead into the plenum chamber where another pipe takes it to the servo. Just before the pipe goes into the grommet, there is a small 3-mm fabric covered vacuum hose on a bulged section (which is a non return valve) which goes to a Y piece that sends the vacuum off down to the N75 valve and in the other direction to the EGR valve control solenoid and also to the shut off flap solenoid. Pull the small hose off of the servo pipe (be gentle, or you could snap the pipe off and then need a new servo pipe) and suck on the small hose.

If you are stuck, tell me and I will take a picture of one I just finished putting a new head on yesterday as it is still on the ramp waiting for a road test tomorrow before handing it back. He will get a shock when he drives it as it came in for losing water but had no power either which he didn’t realise as he bought it like that. It is quite nice to be able to give it a major power increase for no cost as he will have some tangible benefit for the couple of thousand pounds fitting a brand new head/valves/cam/lifters etc has cost.

A picture would be be very useful if it's not too much trouble. I've just been out and had a poke round. Took off the big rubber pipe that goes from the air box into the turbo, checked vac tubes going into the n75. Also removed the coolant reservoir - couldn't see anything obviously worn down there. I wasn't able to follow your instructions to the letter though, so a pic would help a lot I think.

I'm having trouble thinking of a scenario how the car seemed to be fine when I reassembled it excluding the snorkus and engine covers. I've had this problem for ages, I'd forgotten how awesome the car feels at full power. Sadly, the fix was short-lived.

Thanks for your help (& patience!).

**Crasher** · 28-09-2008,11:45 PM

Remind me tomorrow or I will forget, short handed next week.

**fullerlee** · 29-09-2008,08:06 AM

Originally Posted by Crasher

Remind me tomorrow or I will forget, short handed next week.

Reminding you now!...

Don't know if it's any easier, but I have attached a diagram I found via google. It's unlabelled, but I was hoping if you could fill in some of the names, I could identify the part you are referring to from that?

Cheers,
Lee

**Crasher** · 29-09-2008,11:24 AM

Your picture, not mine so it's not my fault

**fullerlee** · 29-09-2008,12:04 PM

Originally Posted by Crasher

<pic1>

Your picture, not mine so it's not my fault

<pic2>

Great thanks, will give it a go as soon as I can.

**fullerlee** · 03-10-2008,07:52 AM

Well it finally stopped raining long enough for me to be able to try this.

I disconnected the small fabric covered hose and sucked on it. Then i held the vacuum against my lip and it held fine, held it for a while. Unfortunately I don't think this is the problem.

Thanks very much for all your help.

Next things to try:
-N75: I think I can try to make this cycle using vag-com. Whilst cycling I need to listen for clicks and look for the VNT actuator moving.
-Leaks in the intercooler area: I think the test above is for the small vacuum pipes pre-turbo. I guess the next thing to test would be down-pipe to intercoolr - anyone any ideas how to test this?

Thanks,
Lee