This weekend I will do a thorough scan with DIS V57 (now I have the V52 one), to see if I can figure out where the problem originates . And maybe I 'll find a colleague with E39 to check my GSM module in his car, to see if it is damaged or the wires have breaks somewhere.
This diagnosis tool spared me of great expense and a very big headache.

__________________
The Ultimate Driving Machine