Brake System

Alright I have a friend with a 94 civic ex, ABS and rear discs, I don't know if thats standard or not. When she starts her car it sounds like a hum, sort of like a bad PCM in a mopar would make, but it seems to be coming from the ABS controller.... Its only stays for about 30 seconds and its only right after the car is started. She said someone told her it was an ABS pump but I'm not too sure, any ideas on what it could be?

Thanks.

theres no such thing as an ABS pump...
and i believe 94 was the first year that the EX civics came with 4wheel discs as an option on ABS models, but correct me if im wrong.