Hi, audioguru. I'd like to ask for a clarification of what you described, as I think I may be misunderstanding it. (Please take no offense; the shortcoming is mine.)
It sounds like you're describing a circuit beginning at 12V supply, through a 4.7k resistor, and through a 100uF capacitor to ground(?) Then connect a 10k resistor from the above resistor/capacitor junction to the ECM +lead?
I probably have this wrong. I see lots of current limiting, but no DC voltage dividing.
Thanks for your patience. Your help is much appreciated, here.