it seems to be a code with many meanings and asked on many sites so ill look into it,
Sample Answer below :
VW Jetta GLI/VR6, 2003
The error code, "P3081" has been identified from a recent diagnostic and I was wondering if you could be so kind as to help me interpret what this code is and how, perhaps, to remedy this problem..if any...
"19537 4C51 P3081 Engine temperature too low"
That DTC is indicative of a missing thermostat, a stuck open thermostat, or a cooling system with 100% antifreeze. It is NOT associated with a defective ECT G62.
When the coolant temperature is too low, that does not necessarily mean a sensor failure. Sounds like the sensor is telling you the truth.
Watch the temperature on the scan tool as the engine warms up. Look for things that keep it from warming up. Things like radiator fans on all the time, straight anti-freeze, stuck open thermostat and so on. That is what it means. It means a system problem, not necessarily a component failure.