I have a 5Litre EB Fairmont, its a bit of a funny story, as it is fully optioned with all the gia stuff but has no elec windows, but has an elec sunroof.
If the trip computer is anything like mine, it will beep when you press the buttons, did you test the buzzer thingy that is meant to beep to see if it beeps ??? Give it a go.
Mine beeps at me for all weird reasons, at 80,60,40 and 20'k's left on the fuel meter, it beeps and it really shits you off cos you have to hit the reset button on the trip comp to shut it up,by the way if your like me and want everything to work I understand, but hey, if the rest works just leave it :o) its not as if your really missing out on much and its only a high temp fault, if you need the bloody thing to beep at you to tell you that your cars running hot.
Anyway, thats my 20c worth