Old user new car issue

Please confirm my issue and resolution.

I have a 1998 Passat B5 and can use my iso-com interface on it.

I have a 2003 Golf GL and have not been able to talk to it.

I have a Key-USB interface and still no luck. on the Golf.

Now have a 2015 Golf TDI -AU and the Key-USB interface connects and says no CAN support.

SO as I read the interface guide I need to upgrade to the HEX-USB+CAN in order to talk to all 3 cars.

Correct???

Suggestions?

Yes, a HEX-USB+CAN would work on all three, but it is obsolete. Current interfaces are here and are universal.

I'm not sure what's up with your 2003 Golf. Both the ISO-COM and the KEY-USB should work on that. If they work on the 1998 Passat, then I'd say there's something wrong with the Golf. First thing to check: Do you have +12V on pin 16 of the diagnostic socket?

-Uwe-