Step 1 does your speed control operate correctly? Verify that all functions operate properly. If yes than next thing to do is.
Locate the part number of the currently installed ABS Module and compare that number to what is currently available. (this would be located exterior under body, under the drivers seat, covered by a shield, has brake lines running into it). Does the vehicle have the latest ABS module installed?? If NO.. Install a new ABS module. The Hydraulic control unit might need replacing too if moisture is present, located with the ABS module.
If yes to the lastest ABS module...
Next simplest thing to do is Key in OFF, disconnect ABS Module C155 Connector (only one on module, yes shield comes off). Key in ON position. Measure the voltage between ABS Module Harness, Light blue/Red wire pin #6 ( harness will have 3 rows of pins, 2 rows close together at bottom and 1 row at top, its the top row, 6th pin from the right)on harness to ground while pressing and releasing the brake pedal, with brake pedal released there should be greater than 10 volts and with the pedal pressed there should be 0 volts. If this is confirmed true, Install a new brake pressure switch.
If the voltage test is not confirmed than you need to troubleshoot the pin #6 circuit for an open and verify that fuse 18 (10amps) fuse in Smart Junction Box is okay. | 
Linear Mode
