I don't think it's that simple. Pin 1 is data, not output. I'd guess it's a TTL level signal and not what you need to drive a Sonalert. The buzzer output on the EZ-Steer controller is first sent from the 500 on the CANBus, along with a whole bunch of other stuff on those four wires and then the controller seperates it out and makes an output level that drives the buzzer.