MarkT:
Can't really figure out your description of the resistive divider you have there - 10k and 22 ohms in the same divider setup sounds unlikely to work to me. Why not use about 1k from 5V to the analog pin and the button pad from there to ground? Why two 10k resistors in the first place? Is anything else connected to the button pad leads?
I've attached a schematic to clarify. There's only one 10K resistor -- one end is connected to +5v, the other end to both the A0 pin and the button interface. This measures the middle of the voltage divider formed by the 10K resistor (the known quantity) and the button interface (the variable).
I don't know the implementation details of the actual button cluster in the car, but I've set up my breadboard to mimic the behavior. The buttons, with their respective resistances, are all in parallel with a 4.7K idle resistance. When a button is pressed, the total resistance should equal the labels shown in the diagram. (I.E., the button resistors may or may not be the values shown -- but should manifest as that resistance when paralleled with 4.7K.) The circuit in the car may have dual-pole switches to cut between them rather than parallel them. Same end result either way.
Hope that makes sense.
@Udo: Thanks for the reference material links! I'll dig into them this afternoon.
