just track the wires back from the motor that's spinning to the pcb connector. the pcb can only do one of two things... 1. constant power with ground path switched on/off. or 2. constant ground with power switched on/off. If you measure the voltage going to the motor and track those wires back you should discover which it is.
I would assume it's switching the ground path on/off electronically and that component is bad. Maybe look for anything burnt looking near the connector. It could be a multi transistor array in a dip package, hard to see with the pcb angle