JAB66

I'm a bit embarrassed to post this since I'm sure this has been discussed 1,000 time, but I can't find a relevant post. So the combo is suspension warning light on, suspension locked at third height setting (but not losing air), and traction control apparently out (pressing ESP button does nothing). I don't have the codes, but based on what I've read, I think this is the sensor that controls these two and the headlight leveling. Know how to fix most of the issues ('01 with 210,000 miles—been through most of it) but this a new one and I don't know the fix. Anyone know the repair and approximate cost?

PaperToast

one of the best things you can do is either 'a', makes friends with someone with a vagcom, or 'b', get one.
takes 99% of the guessing out
several things come to mind as well from hanging out on the forums for almost 10 years, but again its just a guess without the exact codes

fill out your location, there might be someone close by who can help out
nothing super specific, just city and state works fine

John535is

Agree with PaperToast about vagcom.
Without it, only 2 things come to mind (this is the 1% guessing stage).
1. If you want to test the levelling switch, you can swap it with the one on the right side or the back ones, the actual switches are all the same, its the mounting and the little plastic arm that differ. From memory its like 2 * 8mm bolts or something, give the area a bit of a clean, its pretty self evident. Take your time, they are plastic. The switches are really expensive so you don't want to just start buying parts on a guess. The other thing you may notice, if the switch has failed, your headlights are probably pointing low.
2. Is it the ESP and ABS warnings on?, are your back brake lights actually illuminating? You could be chasing 2 problems, the second being the brake light switch. This is an easy one, especially if your a contortionist. the brake light switch is under the dash on the brake pedal arm. cheap to replace, (like $20). Use genuine, I have replaced a lot of these and non genuine is really hit and miss, and you will pay $10 anyway for a potentially dodgy one so my advice, buy genuine. On all the cars I have replaced, these switches seem to last about 10 years. There's some write ups on guys who have attempted to repair them, I'm getting to old to climb under the dash twice.

Adam's Dad

If you want a cheaper alternative to VCDS/Vag-Com, try OBDeleven.com
They sell a VAG-specific OBDII Bluetooth transceiver that you control via an app on your Android mobile device. The basic app is free on Google Play, with a pro version that you can buy. Google the transceiver for the best price. Some retailers bundle it with the pro app.