C1218 Buick 2000 Regal Antilock fault

Buick 2000 Regal with 3.8L, V6, 85K miles had antilock warning light on. The fault code is C1218. Is the pump bad, or the brake module bad, or wiring fault? How do I troubleshoot this?
I can give you the flow chart for this but most of the tests require a bidirectional scan tool. Do you want it?

Circuit Description
The pump motor is an integral part of the Brake Pressure Modulator Valve (BPMV) . The electronic brake control relay supplies voltage to the solenoid valves and pump motor. This voltage is referred to as the system voltage. The electronic brake control relay, located in the EBCM, is activated whenever the ignition switch is in the RUN position and no faults are present. The electronic brake control relay remains engaged until the ignition switch is turned off or a failure is detected.

Conditions for Running the DTC
 

• The pump motor is commanded ON.
• The system voltage is greater than 8.0 volts.

Conditions for Setting the DTC
Either of the following conditions are present for greater than 0.16 seconds.
 

• The voltage across the pump motor is less than 8.0 volts and the commanded pump motor voltage is greater than or equal to the system voltage.
• The voltage across the pump motor is 3.0 volts less than and the pump motor voltage and the commanded pump voltage is greater than or equal to the system voltage.

Action Taken When the DTC Sets
 

• ABS/TCS is disabled.
• ABS/TCS indicators are turned on.

Conditions for Clearing the DTC
 

• Condition for DTC is no longer present and scan tool clear DTC function is used.
• 100 ignition cycles have passed with no DTCs detected.