My printer just had the same problem today. Being an electrician, I started immediate diagnostics. I found 12v incoming to the extruder at the wiring harness, and continuity through the other side of the harness going to the extruder heater (i assume). So i tried putting it into nozzle cleaning mode so it would try to heat up the extruder. As I wiggled the harness back and forth, it would sometimes catch a good connection and heat, but if I let go it would go right back to not-heating. Loose connection. Sure, you can void your warranty and snip wires and solder them (or better yet for ease of change out in the future, wire nut it) to bypass the harness... or you can just shove a knife blade or flat head screwdriver in the side with the pins and bend them a little up or down so that when you reconnect the harness, the pins make better contact in the pin socket.
On a side note, i sent a message to XYZ support letting them know what I found, and asking if splicing the wires would void the warranty. They apologized for the problems I was experiencing (fyi, apologizing never fixed a single electrical issue ever), and they asked if I made sure the connector was plugged in well (I guess they didnt even read my email). They also advised that the sensor wires could come loose if they were strapped (by them at the factory i guess) too tight. Suffice it to say, I fixed it myself. I may have issues in the future with it, and if I do, I probably will just splice the wires with wire nuts (Cuz that's how we do it in the hood, G)
Aaaaand... mere minutes after writting this, the problem reared it's ugly head again. I snipped them and wire nutted them. Peace out