As I was on my way to the mall for christmas shopping, my ABS and emergency brake lights come on and stay lit up. After about 5 minutes of the lights being on, the brake pedal goes hard and then goes to the floor! No power brakes! Good thing i was in a parking lot when it happened. So after a few minutes of playing with the pedal, both lights go out and the brakes go back to normal. So i continue on cautiously. Then the lights ABS andf emergency lights come on again. 5 minutes later the brakes die again. This happened 3 times while I was out. I dont want t drive the car like this in the winter. what would cause this? And what would it cost to fix?

Am assuming you have a TEVES since posting here. First thought (and about the cheapest) is the boost pump relay ($12) not closing when it should. This lets the pressure drop low which turns the red light on and when the red is on, so is the yellow.

That said if the accumulator were good, you should have up to 20 stops after that before the boost goes away so probably need one of them also ($100).

Just my thoughts from very limited information (your service manual should have a complete decription and diagnosis in section 5).

Note: few GM servicemen understand the TEVES since it is German and GM only used for a few years (basically 88-90),. If must go to a dealer, try a VW or SAAB center.