My mk2 has for the 3 years I've had it never been able to reach the middle of the temp gauge where it should be. It very slowly reaches 1/3 if I drive on the high way for a long time.

In the winter it is harder for it to go even 1/3 up and it has thrown p0115 (ECT sensor) fault codes a couple of times. I stuck an OEDB live reader into the car and drove and the temp. seems to go to 90 C which should be fine?

If the ECT sensor was at fault, then wouldn't the OEDB reader give me a wrong reading? The reading also matches the outdoor temp. before starting the car.

What could this be if not the the ECT sensor?

Hi,
What engine does your car have and what year is it? On some models the gauge and engine control unit have different sensors. Also unless you are using Fiat specific diagnostic software like www.multiecuscan.com the fault code descriptions can be misleading.

Robert G8RPI.

1,2 8v gasoline from 2005.
Or from wiki:
SPI 1,242 cc I4 60 PS (44.8 kW; 60 hp) at 5500 rpm 98 N·m (72 lb·​【33 kg】ft) at 3000 rpm 9.6:1

The thermostat should *begin" to open around 88-90 degrees. So it seems your thermostat is broken. With the cap off the car boils the coolant at normal temperature.

The electronics have got nothing to do with the engine temperature other than turning the fan on when it is too hot.

The termperature gauge begins to move at 50C. I suspect your top hose is already very hot at that point because the thermostat is open. 48C is hand hot - the max temperature you can still have your hands in water.

I changed the termostat and it fixed all my problems!
The car ventilation is also much better now since it does not take 2 h before i get heat in the cabin. Thanks!