Usually, if you unplug the coolant temp sensor, the fan will run. If you turn on the ac, the fan will run.
You can take connector loose from fan, if two wire connector, use jumper wires from battery for voltage and ground to connector, see if fan will run, if not, suspect a faulty fan. You probably should use an inline fuse on the jumper.
Any applicable mil codes, you can check those codes, yourself.