Worth plugging in for that one. I don't have those gauges and I can't remember whether they actually use a sensor or whether they're simulated from coolant temp etc (I seem to remember something along those lines).
Coolant temp sensor would cause the radiator fan to kick in, so I reckon it might be that, but without actually checking the data I can't say for sure.
I'll have to plug mine in to check if there's an oil temp/pressure reading on OBD but I don't remember seeing one.