First off the 1999-2000 stock head units are not compatible with the 2001- head units (something like that), so knowing what year your Alero is might help, since the wiring is different.
Anyway, if this extra Scosche piece is plug and play, what happens if you switch it back?
Link to actual product please!
Is it this one:
http://www.amazon.com/Scosche-GM2000...dp/B001CXCJC6/
Or maybe this one:
http://www.scosche.com/car-audio/ins...tors-interface
The reviews say to get the Metra adapter!
http://www.amazon.com/GMRC-01-Axxess...dp/B00032AIGG/