There is also a possible loss of communication with the ABS module, or problems with the ABS power supply or power relay. Scanning would be the fastest method of diagnosing the problem, but checking all fuses and for signs of moisture intrusion into connectors might also be prudent.
The EBCM is mounted to the inside of the left frame rail, right about under the driver's floor section. The electrical connectors and ABS power relay there could be wet.
