I have an Arduino Uno and circuit that controls a car exhaust valve with an rf receiver. The Arduino is powered by a 5v USB charger and the circuit has a momentary switch & led that operate an rf transmitter. It is an independent solution.
What I would like to do is utilize the dash switch & led. Diagram is below; A2 (T31) is ground and A3 (T15) is 12V. I cannot isolate the switch as they are one circuit board with other switches. When switch A10 is closed 12v gets passed through. To illuminate led A11 ecu grounds it.
For the A10 switch I am planning on using a voltage divider to allow the Arduino to accept the signal.
What is the best way to ground the led?
I assuming I need to connect the ground A2 to the Arduino ground as well.
Any input would be apricated.