Get an LM3914 IC wired as in the attachment. Connect a resistor between pins 6, 7 and pin 5, and then connect the output wire from your steering wheel to pin 5. Pick the resistor so that when the button with the highest internal resistor is pushed, the resulting voltage divider produces an output voltage of about 3.5V. The other buttons, when pressed, should create output voltages less than 3.5V
If all of the LEDs were hooked up, you should get four different LEDs to light as each button is pressed. If one of the buttons straddles two adjacent LED states, diddle the resistor to move the ranges a bit. Now substitute pull-up resistors for the four choosen LEDs, and hook up a transistor and relay for each of the four...