Why won't my rodeo turn over when ECM replaced with a compatible used one?

correct it won't crank at all... no starting turning... from I've read on AllData indeed the PCM does need to be reflashed with lastest software if changed whether compatible or new. I'm just not sure if it is the PCM or if it's the electronic trottle body that's not functioning correctly. It hasn't thrown any codes now like multiple misfire nor has the loss of power light come on, although I haven't taken it on the highway.. Is there a way to check the original PCM, because when I put that one back on after realizing the used one needed flashing, It works, car starts as always, just still trottle not opening correctly, dumping fuel as I got a whopping 122 miles to this last take of gas. YES TANK (16gal). I'm just at a loss at this point. I redid both heads and head gaskets when I got this thing. After replacing timing belt, water pump, thermostat, head gaskets, valve seals, EGR, cams seals and valve cover gaskets it started getting hot every time I went 3-4 miles. It never completely overheated as I was very diligent in watching the therm. Turns out the machine shop did not cut valves correctly. I removed heads,the machine shop redid valves correctly, and that issue was corrected. Hasn't gotten hot since. BUT, wondering if the number of times the temp rose, if it may have damaged or made throttle stick or the sensor below pedal bad.. I just don't know. Also can't find place to reflash any PCM. Evidently there are only 2 dealers in VA and they aren't in Richmond. SO..... there it sits for another week in my driveway! HELP!

Do you have access to a *good* scanner... Like... Snap-On Modis Ultra for example... One with live data and functional test capability?

yes. i can get ahold of a snap on reader.. then what? I guess with that I could do individual component testing... I should've thought to use a more sophisticated reader... it didn't really cross my mind. Hopefully that will show whether is the system vs. sensor or computer.. Thanks for for the suggestion. Please check back at end of the weekend, I may have another question for ya !!

That's the only way to go on this one!.. Can test APPS to TPS sync to see if all is well plus a list of other component testing and live data readings... Good luck!