No, when I'm checking for on/off I have the car power connected to a 2 resistor voltage divider. I use vehicle power, 10K Ohm resistor, 3.3K Ohm resistor to ground. Connect a Fusion Brain analog in to measure between the two resistors. It will normally see about 3.5V with car running. The 5v out and ground on that FB analog input port are not connected to anything. Set your software to turn on output for anything over 2.5V.
Keep in mind most alternators put out just over 14V when the car is running. The 10K & 3.3K divider will protect the brain up to 20V. I've seen as high as 18V when having charging system problems.
If you have your heart set on using the digital input, connect the back-up light power to a relay. The relay can then close a circuit between the digital 5v out and input pin. You will then need your 1K ohm resistor to pull the input pin low to a ground.
Get the $13, 500 piece resistor pack.