This is in regards whether or not the vehicle has SiriusXM factory. The customer should know if they did, but there's a chance they may not know.
If you run the VIN in for the RPO codes, the next steps will assist further.
To find out if the customer has the SiriusXM factory, search for the option code "IBBAB0".
If the option code IBBAB0 is present, then the customer will be using the GPS/XM Splitter harness SKU: F-SATSPLT-S1 to utilize both Sirius XM and GPS.
If the option code IBBAB0 is NOT present, then first check for "IBYAD0" but if that also isn't present then the customer will just need a GPS antenna SKU: F-GPSP to obtain the navigation signal. If the customer wants to add SiriusXM and GPS they will need the F-GPSP and the universal SiriusXM antenna SKU: U-SATMAG.
If a customer does have option code "IBYAD0" then they have a separate module that controls XM to the radio. This is also where the XM antenna's yellow fakra is plugged into. Not into the back of the radio but this module that is located behind driver's knee bolster.
Picture example below. There are to plugs to this module. Behind the black connector is the yellow/curry fakra for the XM antenna.