2006 A6
 

I recently had my abs light come on. My mechanic says my abs module needs to b replaced . does anyone know a place i cane find a cheap used 06 A6 ABS module ?

You can have your present ABS module repaired by several nation-wide companies.
I just had mine done by BBA Reman for about $200, inc'g 2nd day air UPS shipping each way. I bought their service through eBay, $157 vs $350 if I had just used their service directly.
Lifetime warranty on the repair.
Some others recommend CheapABS.com too.

The best part is that you do not have to disconnect any brake hydraulic lines to pull the ABS module. I followed a CheapABS video to do the job myself. I pulled the module on sunday, shipped it out on Monday, got it back on Friday & put it back in on Saturday. I did pay an extra $40 for expedited shipping, but that saved 2-4days in the process.
You can even drive the car without the module in place, although your speedometer, abs, esp, etc. will not be functioning. I when about 400 miles while my module was out.
To replace the module is more cumbersome & usually involves recoding some software on the car. The module has to be a direct match for the model, options & configuration of the car.
Good luck & get yours fixed.