So the service manual places the tuner inside the AV radio unit? My Navi radio has it outboard. I'm not an XM engineer but it certainly is possible to put the XM Chipset onto an OEM PCBA and XM will approve it, but it requires MUCH more work for all the tweaking and so forth for SAT s/n ratio, all the communication between devices on the XM block diagram and so forth if it's done by the OE maker. Million times easier to use outboard module.
Your tech guy is correct, unless there is an issue with the XM chipset itself in the one small place that the paid/unpaid bit is stored (which is highly unlikely) then if the radio recalls presets then it seems it is retaining BAT memory NVRAM contents.
I've thought about it more and since the trouble began when you put other stuff in the signal path maybe, just maybe, something got damaged. If you had done NOTHING before this happened I'd say too bad, but now this happening after doing all the work is probably not coincidence.
PS: Guys sell those radio here all the time (non navi ones) so you could pick one up here in parts classified if you wanted to, or just put a 2 DIN headunit in there with XM built in. Many many guys have done just what you have done with no XM side effects reported. Very strange.
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