I currently have an aftermarket remote lock/unlock system for a car. It works by triggering a Bosch relay that triggers the door lock. I have developed an Arduino Uno app that will allow me to trigger the Bosch relay from an iPhone. I found a electrical schematic on the Henry’s Bench website for using the Uno to control the Bosch relay. The schematic below is my proposed interface between the existing remote system and the Uno/iPhone system. Both systems close ground to activate the relay.
I am a true electronics novice but is there going to be a issue with activating the relay (Bosch pin 85) from 2 different sources?