Is it possible to use one engine coolant temperature sensor to provide an accurate signal for two separate recievers(ECMs)? Such as splicing the 5V ref wire and using that to supply a signal to a separate computer.

Or is it just not possible and I need to use two ECT sensors?
TIA

 

Just for safety in isolation, I would try to avoid tying the two sensors together. The grounding and sensor signals may not be a problem, but connecting the two regulated 5VDC logic sources from two ECMs may be a problem. I've never investigated the possibility, but I suspect it could cause trouble with either or both ECMs.

I have no idea what you are doing using two ECMs on one engine, but it sounds like you are working on some cool theory. I can only guess...