It sounds like you have a door sensor. With the harness un-plugged it thinks the door is open, when it's not even attached. It's for safety, if it's just an on/off switch setup, you could jump the pins on the wiring harness.
Could you tell me exactly what jumping the pins means? Thank you for all your help.
Connecting the two wires. Do it with a small fuse in the middle as a test, just in case it's a dead short. There is no dealer around to ask, as there must be a way to operate it with the door off. I have never worked on a Cat so ask a few people. Ken
Hey Bud, you have probably got the door sorted but for anyone interested as I was not too long ago. You pull the pin, on the male side with the connector orientated to the top, you will have 6 holes, you have to jump the middle left with the bottom right. Basically, a bit of good wire between the two. The door wriggles up and off. This was on a 247b '06' model anyway.