What have I done?

Long story short: While changing front struts, I removed two brake lines (from master cylinder to ABS module) in order to access one of the strut mount nuts. I finished installing the struts and then put the brake lines back on. Of course I need to bleed the ABS pump. Hooked up VCDS but it won't see the ABS module. It also cannot see the Transmission Control Module and some other stuff. (I will post a scan next but want to get this in front of some eyes quickly.)
In poking around the engine compartment I noticed a thin red wire coming off the + battery terminal that looks like it was broken. I had also pulled the battery out during some of the work I've been doing on the car not related to the struts, and I'm thinking maybe I accidentally broke a connection to something important. Here is a link to a picture of the mystery wire in question circled in yellow: https://goo.gl/YJEcDy
I cannot find where it might have been connected. Unfortunately I don't have the Bentley or any wiring diagrams so I am hoping someone can help. Where does that wire go and could it be causing my problem?
(There is also a connector that seems to be a dead-end (circled in black). Thinking that may be related to the 5-speed swap the PO did.)

The more I look at the battery compartment, the more I think that the red wire supplied power to that pigtail connector circled in black, and that when disconnecting the battery I inadvertently yanked the wire out. However, I am reluctant to just try putting power to that connector without someone a lot smarter than I confirming it. In my experience, energizing things that are not supposed to be energized often has serious negative consequences including but not limited to sparking and melting and burning...

Yes I understand the red wire is not factory but was thinking it's related to the swap. I didn't save the scan but I believe it also said something about no communication with instruments. (I may need to put the battery back in and run a full Auto-scan.)
There is no ABS light on. No aftermarket radio or trickle charger . No aftermarket anything really. All stock except the 5-speed.
That power lead got yanked from somewhere and I can't help but think some module or modules are not getting power and therefore aren't communicating with VCDS.

QuickTD said:

You're not going to communicate with anything without the battery, or did I read that wrong?

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Of course. I was running the scan with the battery in place and connected. While looking around trying to see what was causing the problem, I spotted the red wire with the bare end. I pulled the battery to see if I could figure out what the bare end was connected to. That's when I snapped the pic.

QuickTD is correct. That red wire is aftermarket to power something else. I would remove it so that it doesn't short out.

Have you checked your ABS fuse? IIRC it is either 10 or 14

Quick Update

Removed red wire. Reinstalled battery and now I DO have an ABS warning light. ABS fuse is good. Ran full Auto-scan, cleared codes, and then ran another full Auto-scan. Here is a link to a pdf of the scan: https://goo.gl/zi988f
Besides the Transmission Control Module no communication fault that you guys have explained is due to the 5-speed swap, the remaining one is "01486 - System Function Test Activated". Looking that up on the Ross-Tech site, it says that the system will set the code whenever major brake work is performed. In order to clear it you must successfully perform the ESP System Function Test.
The first step in the test is to "Firmly press the Brake Pedal until a certain Brake Pressure (usually right above 30 bar) is reached." Well when I do that, the brake pedal goes to the floor, which I assume is due to the fact that the system is full of air.
I am thinking the next step is to bleed the system the old fashioned way. (Open bleeder screw, depress pedal, close bleeder screw, release pedal). I'd rather try it with my Motiv power bleeder but from what I have been reading, it may not develop enough pressure to push air through the ABS module. Thoughts?
Am I on the right track?

You can use the Motiv IF your brake fluid reservoir has not deteriorated to the point of not pressurizing. The like to "rot/crumble" in the back left corner (passenger side). Go easy on pressurizing (10-15#).

vwztips said:

You can use the Motiv IF your brake fluid reservoir has not deteriorated to the point of not pressurizing. The like to "rot/crumble" in the back left corner (passenger side). Go easy on pressurizing (10-15#).

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Mine seems to be in pretty decent shape, but I will be careful anyway.

One more dumb question: I probably need to bleed the clutch slave cylinder, but have been unable to locate it. Where the heck is it? Do you bleed it from the top side or underneath? Can anyone give some directions to find it?

The nightmare continues

Manually bled the brakes (in, out, in, out) in the prescribed order (RR, LR, RF, LF) and got lots of bubbles (as you would expect with removing 2 brake lines). I bled each corner until there were no bubbles and the fluid was clean. I am confident that I bled them long enough to assure that I was getting new fluid from the master cylinder. I actually went through 3 quarts of fresh fluid.

I put the wheels back on, pushed the brake pedal, and it goes straight to the floor! Pumping it quickly builds a little pressure but only for a split second and then the pedal goes right to the floor. It also doesn't even come all the way back up. Unless I manually pull the pedal back up, the brake lights even stay on! I suspect but cannot confirm that the old school bleeding has left air in the ABS module. I would like to bleed the ABS unit using VCDS, but VCDS won't operate the ABS pump until I perform the "System Function Test" and the car won't perform the test unless I can build pressure in the system. An endless do-loop as we used to experience in the programming world.

I am at the point of complete exasperation. My daily driver has been off the road for a week and I have got to get this car back. Can anyone tell me what is happening here?

I've had this before on B5 & Mk4. It's a PITA. I always make sure I never let the system run dry anymore. I usually have to run the ABS bleed to clear it.

Maybe the B5 is just telling you to go drive the W12 and enjoy it! I had mine out this week.

Uberhare said:

I've had this before on B5 & Mk4. It's a PITA. I always make sure I never let the system run dry anymore. I usually have to run the ABS bleed to clear it.

Maybe the B5 is just telling you to go drive the W12 and enjoy it! I had mine out this week.

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If it's telling me to drive the W12, it does not realize that the W12 is infinitely less reliable than the B5. I've owned it for about 9 months and it's been roadworthy for maybe 5 months tops.

Anyway I badly want to run the ABS bleed, but it's stuck in the "System Function Test Activated" fault which can only be cleared by running the test. And you can't complete the test with no brake pressure. Any idea what to do next?

Are you positive that you didn't lose your brake master cylinder in this process? It's old, probably original. I replaced one of my rear hoses due to me snapping a brake line trying to bend it out of the way to remove the bolt for new rotors/pads. I did not have any abs issues. I bled the rear brakes and was done.

QuickTD said:

Dude, it just ain't that bad. Don't be a victim. Bleed the brakes like normal and complete the test when you get some pedal. I've never found the abs pump procedure solved any bleeding problems anyway. Stop pulling the battery out looking for trouble, that just creates more faults. For future reference, make like a mechanic and bend the brake line a bit to access the bolts, it'll save you days of agony...

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Thanks. That was very helpful.

PickleRick said:

Are you positive that you didn't lose your brake master cylinder in this process? It's old, probably original. I replaced one of my rear hoses due to me snapping a brake line trying to bend it out of the way to remove the bolt for new rotors/pads. I did not have any abs issues. I bled the rear brakes and was done.

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Thanks for that. No I'm not sure I didn't lose the master and that's what I'm leaning toward. Gonna first bleed the whole thing one more time and see if I maybe didn't get all the air the first time for whatever reason.

Brakes are back

Bled the entire system again. This time I made sure I removed another 6 oz. or so after seeing the last bubble, and that seemed to do the trick. The brakes feel normal.

The only remaining issue is that the pedal does not come far enough back to turn off the rear brake lights. Pulling the pedal about 1/2" turns it off. Not sure if there is a spring that assists pulling it back. I was also chasing a water leak last week pulling up carpet and removing and installing trim. Maybe I didn't put everything back exactly right. That's tomorrow's project.

In theory the main lines all should bleed fine if the valves are open. But oddly I've had a few cars where it seems to help if you run the ABS bleed cycle. I've seen where people make the mistake of opening the bleeders too far and air leaks back around the threads with a traditional pedal bleed.

Good you sorted it.

ps I don't drive the W12 out of towing range That would be just too tempting for the VW gods to wreak havoc.

To my knowledge there is no assist spring on the brake pedal, only the clutch pedal. There is an adjustment on the pedal push rod if i remember correctly. Sadly i just removed another 5 speed pedal assembly less than a month ago and cant remeber 100%. When i did my conversion i had to adjust both the rod and the switch for the brake light so it worked properly.

You never want play between the pedal rod and the cup in the master or you'll have spongy brakes(on non abs vehicles anyway) im assuming the physics are the same.


Ive done dual reservoir master cylinder conversions on old widow maker single reservoir vehicles as well as drum to disk brake conversions (manual brakes not power assist) over the years the info gets fuzzy in the memory bank from all the projects. The more i type the more it comes back to me.