3.0 Coolant light coming on, no overheating, coolant level fine

[Alexhart711]

Hi, so I've got an 03 A4 3.0 q, and the coolant light has recently started coming on and staying on. The engine temp never goes above the halfway point(regular operating temp) and there's no leakage of coolant as the level has remained constant. The expansion tank shows the same level (directly between min and max) when the engine is cold, so what could be the issue? A level sensor? Do I need to replace the whole reservoir? Thanks in advance.

[Tongpo]

I suggest you start by looking at the coolant level sensor, which is located underneath the expansion tank.

Could be a bad sensor or bad wiring to the sensor. One of the wires going to my sensor broke a few years ago due to age and stress. IIRC, this caused the coolant light to come on.