I bought some lights that go into the door of your car and it will display a logo on the ground when you open the door. I have the shop manual for the car and I want to tap in to the "door open" signal from door latch to the BCM. From the schematic it appears that this is a pull up resistor type signal. There is a relay in the door latch which closes the circuit to ground when the door is open.
I'm thinking the simplest way to wire the light is to tap into an available positive battery circuit with the ground of the light attached to the signal circuit. When the door is open the relay will ground the signal line and the light will come on because the light circuit now has a ground. My question is can I short out the BCM by doing this? I'm told the light is actually a laser and draws only a few milliamps and can be powered using a simple 9v battery for testing purposes. I can post a schematic to show the circuit if this doesn't make any sense.
I'm thinking the simplest way to wire the light is to tap into an available positive battery circuit with the ground of the light attached to the signal circuit. When the door is open the relay will ground the signal line and the light will come on because the light circuit now has a ground. My question is can I short out the BCM by doing this? I'm told the light is actually a laser and draws only a few milliamps and can be powered using a simple 9v battery for testing purposes. I can post a schematic to show the circuit if this doesn't make any sense.