Ecm trouble

[np24]

I have a 97 Ranger with a 4.0l. It was originally an auto and I swapped in the manual with the correct ecm.
What would cause an ecm to not read the 3 oxygen sensors and the speed sensor?
I am having this problem with both ecms, auto and manual.
I'm getting oxygen sensor activity at the ecm connector. I checked with a meter.
The speedometer works and the gem won't shift to low range unless the truck is almost stopped.
There is no abs light on and it works correctly.
The only code that comes up is p0401 because the egr valve isn't hooked up. Its a 93 manifold with no provision for it.
The front O2s are brand new.
Could the rear O2 be shorted and disabling everything?
Thanks

 

[np24]

I disconnected the rear o2 sensor hoping that it was the problem. The check engine light came on saying that the heater and sensor circuits were open or shorted.
I'm glad that it's reading it, but it still doesn't explain why the scan tool can't see any activity.
I've tried a brand new action and my bluetooth elm scanner. They work just fine on my car and my dads truck, just not on my ranger.
Did ford do something weird with the sensor data for this year that makes it unreadable by scanners?