The temperature in my audi a3 goes to the normal middle at 90 degrees as normal but when driving up steep hill it goes all the way down to cold, when i drive down hill or level it goes back to optimum temp. Iv had the coolant sensor replaced but still the same issue. Engine code was p0118 but it i had cleared it. It came back once and cleared it again and hasn’t came back but temperature issue is still there
First thing to do would be to confirm the temperature gauge is reading correctly. Use an infrared hand held temperature gun to determine the accurate temperature of the engine.
Code P0118
Engine Coolant temperature sensor 1 Circuit High Input
If this code comes back you may want to check the wiring harness continuity to ensure a good connection.