ABS and BRAKE light on

Just bought a 95 Chevy Lumina LS and before I even picked it up I had it taken to a shop for the oil leak fix. When I picked it up the ABS and BRAKE lights are on all the time unless I start the engine with my foot on the brake. If I do that the lights come on for a few seconds and then go off until I let off the brake and then they come on and stay on. The brakes work but the abs does not. Any ideas where to start? I drove the car 500 miles home today and that seems to be the only problem. Can the ECM be interrogated for the ABS code and what exactly sets off the Brake light. I am sure it is not the parking brake as I can see a difference in the light when I set it and release it. Any help would be great. I am suspecting the mechanic left something unhooked when he did the oil leak fix but I haven't found anything laying loose yet.

sounds like you have a problem with the ABS module. When they go bad, it will cause a low pressure signal setting off the brake light and ABS lights. That's why the light goes off while you have your foot on the brake, because you're creating the pressure, as soon as you release the pressure bleeds off. It's possible that something was left unplugged, if so, that would cause the same symptoms, as the ABS motor isn't creating any pressure at key on. Also check the ABS relay and ABS fuse, as something that simple could cause your symptoms.