Had No ABS - ABS light on along with traction control, and also glow plug light flashing, no brake lights whatsoever. and engine workshop showing. This scares the hell out of you...I was expecting the engine to drop out any time soon. But its's so simple and cheap to fix.
I have the 2003 Passat estate TDI 100.

From using this site discovered that it's the brake light switch that is faulty.
Got the part from VW for £8 (part number 511 RDW 115 204, this will be different to the one you take out as they have upgraded the part), took the panelling off underneath steering wheel and around the pedals. Found the offending part - right over on the left over the clutch pedal(god knows why) removed the old one(took this apart found that it had shorted on the contacts inside). Fitted the new one. No brake lights and still faut showing on dash. Spent about 3 hours messing about with it - thought that the new switch was faulty. after stripping the new switch down found that it will not engage the plunger rod until it is completely locked into place- and thus will not activate the slide switch within. Sounds easier than it actually is....to get it to lock into place you have to really give it some stick. (This is something that is handy to know as I spent ages wasting time) Once you've cracked getting it to lock in the pseudo key hole it's easy to adjust....you just push the brake pedal in a bit (only so the switch activation plate is about 1 inch from the switch location, lock it in place (listen for the click), then release the brake pedal (which engages the switch (which I think is a reverse switch). Connect up the electrics and check with ignition on that you get brake lights with minimal pedal pressure.

This should help someone out - this is an easy job to do(if a bit fiddly) I'm not particularly mechanically minded - this is a fairly logical task. If in doubt take photos first and make a drawing before you touch anything. I think this demnstrates how much the garages take the proverbial, the part costs nothing but I'm sure they'd charge you for 2-3 hours labour and would probably spend 3 hours trying to diagnose when they know full well what the problem is from the off. My local VW dealer parts counter bloke said that these switches are one of the most common things to go wrong...(big cash cow for the dealerships).