2004 Saturn ION - Just purchased in 'mint condition' with 7,500 original miles. Planning to replace the stereo head unit with an updated one with GPS, Bluetooth etc. I had done the same with my other 2004 Saturn VUE with no issues with the unit replacement. However, I have read online about the ION LOC issue. My question: Does the anti theft deterent respond only within the radio unit or does it somehow engage from the electrical system outside the unit also ? Thanks in advance