High coolant temp - according to AutoEnginuity

[Mister Moe]

I haven't used my truck for a while, but I have been using my AutoEnginuity scanner on my van for other problems so I'm learning a little with each scan. Anyway, tonight I decide to start my truck and scan it. I happened to check the coolant temperature with the scanner and was surprised to see it at over 250°! The truck hadn't been running for more than 5 minutes so it was still cold (it's only 50° here outside). The temp gauge still hadn't moved but according to AutoEnginuity, the temp just kept climbing - I shut the truck off at 280° - that's after not more than 10 minutes of idling from stone cold. I find it difficult to believe that the coolant was really that hot. Maybe a sensor went bad?

So, I wondering - does the PCM get its information from a different sensor than the temperature gauge? I'm thinking it must because if I recall correctly, my temp gauge does work - it just never had a chance to get warm enough to register tonight. I did some searching here but haven't been able find anything yet. I'm hoping someone can help.