Coolant temperature gauge not working and Gauge alarm light on

[Brian K]

Today a light on the dash which can be described as a "Look at the Gauges" alert came on and I saw that my temperature gauge was down at the lowest position. I have a ODBII port connected Scangauge which reads the engine coolant temperature and on an hour long drive it showed a very steady 79-81C coolant temperature - which is normal. The engine ran fine and the heater put out what is should - and not indicative of a failed open thermostat - I think. The transmission termperature seemed a bit low (about 150F on the Scangauge but it is cooling down now so that could be normal).
Does anyone have any idea of where the dash gauge gets its reading from (perhaps 2 different temperature sensors)? Also - any idea of what turns the dash light on for this temp reading?

 

[Mooseman]

It gets from the same place you got it, from the PCM. I think there's something wrong with your cluster, at the very least the stepper motor, but that wouldn't cause the "look at your gauges" light to come on unless there's something else, like the oil pressure.