Not sure what it is but do you hear the cooling fan running a lot more lately in the engine comp? maybe a sensor is going and keeping the fan on more?
You`d need to hook it up to a computer to read the errors or diagnostics.

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X5 3.0D 2003
Mods:
Webasto telestart remote kit
Aluminium running boards
Tv in motion & Aux input lead, Ice>ink to Ipod 3g.
DVD rear headrest screens and dvd sytem integrated in to main tv system via aux lead (watch tv or dvd in front and back)
Homelink Gate Opener, Chrome Grille Kit, chrome tailgate handle, Chrome Guage Rings, Tunit V-CR 086
Standard:
Bluetooth, comms pack, sat nav, sports pack, sports seats, dimming mirror, electric folding mirrors, memory seats, heated seats.