You need to have your vehicle computer read for fault codes. This will tell you/us where the fault lies and we can diagnose from there please re-post with codes?
SELF-DIAGNOSTIC SYSTEM OPERATION
Controller Anti-Lock Brake (CAB) Operation
CAB contains a self-diagnostic system which may be used for system diagnosis. When ignition is first turned on, a system initialization starts and CAB performs a self-check on ABS and Traction Control System (TCS) electrical components. At the same time, valves in Hydraulic Control Unit (HCU) are cycled, resulting in pulsations of brake pedal.
When vehicle is operated and vehicle speed is 5-10 MPH, a dynamic test is performed on ABS and TCS by momentarily turning the pump motor on. If any component is determined to be defective during system initialization or dynamic test, a system fault will set and CAB will flash the Amber ABS warning light located on instrument cluster. On TCS equipped models, the Amber traction control warning (TRAC OFF) light located on instrument cluster, will also be turned on. Both ABS and TCS will become inoperative. If there is a hard diagnostic trouble code such as CAB Power Feed Circuit Failure, the indicator light will be illuminated without blinking.
CAB also contains a diagnostic mode, which may be used with scan tool connected to Data Link Connector (DLC). To enter the diagnostic mode the vehicle speed must be less than 6 MPH. If vehicle speed is more than 6 MPH, a NO RESPONSE message will be displayed on scan tool. If the vehicle speed is above 5 MPH, activation of the valves in the valve body will not be possible. Both ABS and TCS will become inoperative during diagnostic mode.
If a problem exists in ABS system relay circuit, or inlet and outlet valve, a system trouble code will be set for problem area. The Amber ABS warning light will come on steady for hard trouble codes.
Thursday, November 20th, 2008 AT 8:05 PM