997.2 Turbo S does not reach operating temperature at highway speeds

My 997.2 Turbo S is having an issue where it will never reach operating temperature at highway speeds, but warms up normally at slower in-town driving and then stays warm, even on highway. It seems like a stuck-open thermostat, but a little different. Any ideas?

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[Casey at Pelican Parts]

Definitely sounds like a stuck open thermostat. I am surprised that you do not have a Check Engine light on.

- Casey

[Balcora]

The first time the problem happened, I took it in to the dealer for inspection and the car did have two codes, P2181 (Thermostat stuck open) and P3081 (Coolant temperature implausible). They reset the codes, and although the problem persists, it hasn't thrown a code again, yet.

Is it more likely the thermostat is stuck, or both the oil and coolant sensors are faulty? I'd bet the former.

[Balcora]

Just to follow up on this... it was indeed a stuck thermostat. Porsche has a revision on the part (.2) and everything is fine again after replacement.