But the extruder motor should be a 4p connector. because stepper motors require 2 sets of coils to walk from one step to the next. Wig wag the 2 PWM drivers is how stepper motors turn. 2p connectors at the extruder might be the temp sensor, the heater cartridge(both of which can be wired backwards without concern), A extruder fan, a part cooling fan, and some might have a z or x sensor on the extruder carriage. If it is just a simple microswitch it can also have just 2 wires and be ok to be wired backwards. Only the fans would be hurt if wired backwards. And because of the electronics internal to the fans they will not spin backwards. They will let out a tiny puff of smoke and usually that circuit in the mainboard gets burned. For your description you either had the thermistor or heater cartridge plugged in 'backwards'.