Need Help Solving a Sirius Problem
 

I am trying to help someone with a Sirius retrofit. He upgraded the navigation and radio, and stuff is talking and generally working. However, the Sirius module will not "stay" recognized by the radio. The problem is that he has to disconnect and reconnect power to the Sirius module to get the radio to recognize it. If he turns the radio off and then back on, Sirius goes away, and he has to repeat power disconnect/reconnect to get Sirius back. I have seen this problem once before somewhere, but I can not remember where and I can not remember how the person fixed it. Does this sound familiar, and can anyone help?

Here is a rundown of the part numbers and other key background...

Radio PN 65.12-6 988 275 (the latest, according to RealOEM)
Radio is set to US mode
Sirius PN 65.12-0 398 140 (he tried two other modules, so the Sirius module is not the problem.
MKIV Nav Computer running 4-1/71 (OS v. 27.1 CD)

The Car: 1998 750iL. It originally had a PI-Bus CD changer. He retrofitted the CD changer analog audio cable, wired the 3-pin CD changer I-Bus plug, and upgraded to a newer I-Bus CD changer. His car is now the A/V/navigation equivalent to a 2006 X5.

His CD changer works perfectly if he bypasses the Sirius module, so that would suggest that the wiring is good. The CD changer will not work if it is connected along with the Sirius module.

Can you help???