I read a response on a different website where the guy having a similar problem took the car to his mechanic and they changed the antenna.
Another fellow said he solved this similar problem by doing a system reset. After the reset, he downloaded all of the system updates and reset the presets, etc. About 4 hours total but it did fix the problem.
Any numbers on the car's VIN are related to factory fitted equipment only.
To receive Sirius Satellite Radio on the NX501, you can connect the optional SC-C1 Sirius Connect Universal Vehicle Tuner 607SCC1 directly to the head unit's Sirius direct connection (no proprietary interface required), although this is no longer available, or try https://www.sonicelectronix.com/item_91789_SiriusXM-SXV300v1-70-Rebate-3-Months-FREE.html