Ok, I appreciate the effort and scoping very much too

Removes much guessing and wood burning smells.
It looks like a balancing act on the actual resistor. A more refined guess would be 23500 ohms for 2.664 volts when injector is off, and 2.093 volts when in hold. And no promises if your alternator goes out

But it really depends what is getting through to the CPU pin as you mentioned.
It might otherwise need some non-linear circuit that increases the spread between hold and closed.