From what I read it will only trigger if the conditions happens more than once. Meaning you have to turn the car off (park it over night for example) and the same condition has to happen again the next time you drive (without resetting by disconnecting battery). Once you go through a few cycles it will eventually throw the check engine light.

Most likely it will throw a code about System cooling performance (*wild guess*) - which usually indicates a weak or bad thermostat. Without the exact internal code or CEL it's just a stab in the dark. I picked the most common occurrence.

 

dustind, I've had an issue with the temp gauge, may not be the same but similar.
My dash engine temp gauge fails to show a reading. CEL indicates a problem. The code reader returns an ECT (engine coolant temp) error. While the temp gauge sits at the default bottom reading, I can see the engine coolant temp displayed on the code reader. There are 2 engine coolant temp sensors in the motor. The one that reports to the ECU (and seen via the ODBII port with code reader) is at the back of the block, far right side of the motor if your standing in front with the hood up. That reports as sensor #1. Sensor #2 that apparently reports to the engine temp gauge is on the front of the motor between the water pump and radiator. It's actually very hard to access at the water pump outlet compared to the other temp sensor.
I have had the sensor replaced but the problem returns, no engine temp reading and a CEL. Suspect the actual issue is with an electrical connection at the dash/speedo display rather than the sensor itself.

 

Thanks for sharing nice stuff. I suggest you best car service provider. Visit Mr clutch

 

hey i have the same problem in my 08 A3 2.0T. it has 150K and when i clear the code the gauge works for about 2 days and dies again. before i start replacing things i just want to know, which sensor is in the coolant tank? is that the coolant temperature sensor or coolant level sensor?

 

The coolant tank/reservoir has the level sensor in it. The temperature sensor is located on the back/side (driver side) of the engine.

 

Ahmed Hamed, there are actually 2 Engine Coolant Temp sensors. One at the rear of the motor and one near the water pump inlet.
From my experience the one at the rear of the motor (far right side if your standing in front with the hood up) reports as the primary sensor for the ECU. The one between the radiator and water pump reports to the dash gauge. It's the hard to get to one by the water pump that has been my issue, not the one at the back of the motor that is easy to get to.