I took my car in for service a couple of days ago. Prior to taking my car in for an oil change and filter replacement, there wasn't anything wrong with the car. When I drove my car out of the service department and took it home, everything was fine.

The next opportunity I had to use the car was on Saturday evening and again on Sunday morning. Both times when I started the car, the fan was very noticeably loud. The MPG gauge remained at the top at 0, even after letting the car warm up so that the engine temp gauge was in the middle. Furthermore, the entire time the car was running (even when stopped at a traffic light), the MPG gauge would not go down to 'E' as it should.

If I took the fan setting off of auto mode, the MPG gauge immediately went to 'E' and the car was completely quiet as it should be. Once I turned the fan back on auto mode, the MPG went back up to 0.

Eventually after driving the car around, the fan wasn't as loud as it was when I initially started the car. Any ideas as to what could have happened? I'm hoping that something with the car service that was done caused this to happen, because prior to having the car serviced, there was nothing wrong with it.

 

Who knows what went wrong on a car, that has more computers than Apollo landing module...
I say, the only way to fix it is to take her back to dealer and ask them to re-flash ECM. free of charge, of course.
Or, simply do not use Auto mode?
This is why BASIC things like oil and filter should be DIY jobs.