parasitic drain

Hello. I recently purchased a used 2013 Buick Enclave. My lender requires me to have a device installed that can disable my starter & also serves as a GPS/lowjack device. The day after it was installed I went to pick up my son's prescriptions & first, the check engine light and oil light came on...

I have a parasitic drain in my 2013 which I believe I've traced to be a bad diode in the alternator. New alternator is almost $200 so I'm hoping to just replace the diode and be done with it. Anyone know a part number for the diode or how to find it? I haven't had any luck.