The G25 only has an USB plug only. If you want to test it test it on a PC if you don't have the disk that comes with it I think you can download it from the Logitech site (Just checked and yes you can download the disk from their site) under Logitech>(support)this is at the top of the homepage then use the drop-downs to chose the G25 wheel.
What to look for
1. Crimped wires under the wheel and shifter
2. If the wheel is real noisy (here you have to know that the wheel is a little noisy)
3. When testing it on a PC bring up the software for the wheel and check that each button works and doesn't stick.
4. When testing the wheel on a PC be sure you have it clamped down because the wheel will shake (a lot!) when testing.
Hopes this helps.I've had my wheel since the G25 first came out and have not had any problems at all, have read that some have had problems at times.