the check engine light is most likely unrelated to the brake light.

The testing equipment you are referring to is a Obd tool. Looks like this:

You should probably think about buying one. I think every Audi/VW owner should own one if they plan to work on their own car/save money. Basically this adapter/cable interfaces from your car's obd connector to a laptop or computer. http://Ross-Tech.com sells a complete kit for ~$250. You can get a cheaper one witih shareware software from http://www.obdtool.com.

You could also try to find someone who owns a vag to scan your car. Lots of people have joined this database who are willing to lend a hand. Check it out.
Vag Locator

 

great post guys! Is this also in the FAQ's catergory? Don't forget that one will get this light when needing to replace the brake fluid. Has any one used green stuff brake pads?

 

does any of this involve bleeding the brakes or is that only when u disconnect the calipers?

 

no you don't have to bleed the brakes to change the pads.

 

i am gettin emiison control sign . i have 2007 audi a4 quattro. can someone tell me wat can be the issue n wats d solution. ?