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VW MKVII-Mk7 Golf family including Golf Wagon (~ 2015 +) Discussions area for the Mk7 (2015+) Golf and Golf Wagon TDIs based on the MQB (Modularer Querbaukasten) platform.

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Old May 22nd, 2020, 04:41   #1
Join Date: Jun 2008
Location: north carolina
Default 2015 GSW Leaky Sunroof causing electrical issue

First post in a long time. I searched but was unsuccessful in finding anything related to my specific issue.

Here goes:

Last Wednesday we had torrential rains. Wife reported that her GSW started leaking water onto her feet in the drivers side footwell, and that water was coming through the forward interior light fixture.

Next day she gets an MIL/CEL. I scan and it's P148b. Go online and find this 'technical tip from VW': 26-18-04TT

It says that water running down the drivers side A-Pillar from the leaking sunroof drain has caused corrosion on the "TUIL" Connector. That corrosion is causing a short and thus the MIL. And that you have to clean or 'repin' the connector as well as reset the Selective Catalytic Reduction system. I don't have the VAGCOM software so that's another issue.

Problem: The car 'thinks' it's out of DEF and it threatening me with not starting within 600 miles. However the DEF tank is topped off and the car runs just fine.

My question is: what's the most economical way to solve this problem? I know about the Rawtek/Malone $2k solution but that's not in my budget.

[ETA: I cleaned out the sunroof drains and the front left was clogged. I removed all 4 nipples from the ends of the hoses and will now commence cleaning regularly.]

I'm considering a software solution or disassembling the interior to get at the corroded connector. Problem is I can't find anything about a "TIUL Connector" anywhere.

I assume that it's part of the DEF system.

Why put an unsealed connector right next to a sunroof drain line that is known to leak? On an otherwise well engineered and excellent car?
At least put some heatshrink or electrical tape around it since the car can't run if it loses connection ffs.

I appreciate any insight the gurus here could provide on this issue.

My next VW (a GTI) will not have a sunroof.

Last edited by lilredwagon; May 22nd, 2020 at 04:50.
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Old May 22nd, 2020, 20:29   #2
JM Popaleetus
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Join Date: Mar 2010
Location: Connecticut

First and foremost, have you had the sunroof recall service campaign () performed?
2015 VW Golf TDI SEL (DSG, LP & DAP, MIB2 Retrofit, Tornado Red/Titan Black)
2007 GMC Sierra 2500HD Classic SLT (Duramax LBZ, Extended Cab)
2013 VW Passat TDI SEL Premium Buyback
2010 VW Jetta TDI Buyback
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Old May 22nd, 2020, 23:04   #3
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Join Date: Feb 2005
Location: Island near Vancouver

I don't know what exactly TIUL stands for, but it's basically a cluster of connectors in the driver footwell, underneath the pane right where the hood release is.

If my car had the same issues as yours, my DIY fix attempt would be to get at that, separate everything, and spray a bit of Deoxit D5 into the connectors.

Ignore the arrows and extraneous connectors (from ACC and Lane Assist retrofit) I've added in photo below - this shows you what's underneath that panel by the hood release.

His ride: 2015 GSW SEL TDI with MIB2, Active Info Display, Adaptive Cruise retrofit
Her ride: 2016 A3 e-tron

His other ride: 2015 Giant Propel SL Di2

Last edited by Nuje; May 22nd, 2020 at 23:07.
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Old May 26th, 2020, 15:20   #4
Join Date: Dec 2016
Location: northern illinois

Same thing happened to me last fall . Every warning light on the dash lit up . Dealer took more than a week ( and several calls to VW ) to figure it out and clean the harness connection . The service ticket says that I left the window open during a storm . Then in March I get the service campaign letter and have that done . Almost two months later I get in the car after a couple days of rain and 3/4 of the headliner is stained and wet , as is the passenger side seats and cargo area . It's been in the shop since last Thursday . Still waiting to hear from them . I really like this car , but if I had it to do again , I definitely will not get anything with sunroof again .

Last edited by tom61; May 26th, 2020 at 15:26. Reason: add more info
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