Water Temperature "Failure Indicator"

[Prof Beard]

This morning my 996 C4S Tip started normally then a mile or so up the road I got "Failure Indicator" and a picture of a thermometer on the computer, a slow flashing red light on the temperature gauge and a zero temperature indication on the gauge. All levels were normal and the coolant in the header tank was hot/warm when I checked it after a while. The car is (via AA ) off to the local specialists on a truck in a bit.

Ideas, thoughts?

Edited by Prof Beard on Monday 12th November 14:40

[Prof Beard]

Thanks - from trawling around on the forums, there seem to be a number of causes of this - hopefully I'll know which mine is soon once the garage report back