Since last week I am getting a coolant warning in the DIS. It happens about 5 minutes after a cold start and goes away after another 5 minutes. While the message is in the DIS the temp gauge stays at zero and when the error goes away it suddenly jumps to the actual temp. There is enough coolant fluid in the system and the temp does go to a perfect 90 degrees (celcius), so everything seems to be okay. The dealer says it sounds like a faulty sensor (The car is booked for next week). Is the coolant temp sensor the same one as the level sensor next to the filler cap? I unplugged en re-seated that one but that hasn't helped.