I have a problem with my 1995 Tahoe. When starting, randomly, the abs light will stay on. When this light is on, I am unable to use any of the controls on the heater control panel (heat/ac/rear defrost) and can not get 4 wheel drive to engage. After sitting a while, the brake light comes on and then the abs goes off followed by the brake light. Half the time after this happens, I can use the controls and 4 wheel drive, other half the abs light comes back on and I have to wait again. Any ideas what this may be? The 4 wheel drive is on the floor not push button.

 

Turns out it had several ground issues.