Strange fault on BMW X3 3.0D.

[Grindle]

Sitting at the lights yesterday the engine stopped. I noticed that the coolant temperature gauge was way over the top, past the red line. So i assumed some sort of protection device had shut the engine down due to the water temperature. But there was no steam from the engine, no water underneath. So with thick gloves and a towel doubled over twice i removed the header tank cap carefully. The coolant wasn't that hot at all. Within 2 minutes the gauge was showing normal! So i tried to start the car, it started, the gauge flew straight up to and past the red and the engine stopped. Then i noticed 2 warning lights. Automatic transmission light and dynamic stability control light, with a 4x4 symbol below it.
This makes no sense at all to me. Hot then not hot. Starts then stops. Warning lamps lit but related to the drive line not the engine.
I can't imagine too many BMWs have done this but you never know. Has anyone got any suggestions?

[BFleming]

What year / engine? If it's the car in your garage, do I assume it's 2006 and the engine is the M57? Thermostats are notorious for going bad on the M57 engine, and there are 2 of them. There are also a couple of temperature sensors. Hypothetically one thermostat could be closed, meaning the radiator & header tank stay cold whilst the block cooks itself.
I assume also that being a 2006 car you won't have start/stop?
Codes. Have them read for the other faults. It all could be a bad battery, so measure the voltage there too.

[Grindle]

Thanks, it's a 2006 with no DPF (hence £555 chuffing road tax!. That's one way to get people to scrap their ''polluting'' car i guess.)
I've had the faults read yesterday by the local independent garage and the ECU is not playing fair, they can't get it to communicate any faults. So maybe the ECU is dead or dying?
It was just the nature of the fault lights which confused me.

[BFleming]

The lack of communication will be more down to the hardware/software the garage is using rather than any fault of your ECU. Where abouts are you? I'll help if I can!