What year and model of vehicle is it on. For a 2001 Tahoe two wheel drive, it is located on the outside under the drivers seat on the inside of the main frame rail. The electronics module can be removed from the valve assembly without effecting the normal brake system and can be sent off for repair. GM does not repair the module, they only replace at a very expensive charge. Go to www.absfixer.com and check out the procedures. May save you some bucks if you can do it yourself.
It is located on the brake pedal arm under the dash.
daytime running light module under drivers side dash
On my 89 it's right behind the park brake
what does it mean if my brake light is blinking on and off when its pushed down in my 1999 Chevy silverado
Located on the frame under the truck, close to the driver side.
On my 03 Chevy Silverado I just added brake fluid and the message turned off.
under the drivers seat, just inside the frame. you'll see it on top of the hydraulics
a 2003 Chevy silverado taillight bulb uses a 3157
need to find out how to replace a power brake booster in a 2002 Chevy silverado 2500 HD
Try this link: http://www.etrailer.com/faq_cbc.aspx
top of brake pedal