4 wheel drive ECM

I have a 2005 Toyota Tacoma four wheel drive automatic transmission with a 4.0 V6.
I have been having a problem with the 4 wheel drive. The indicator light flashes 4 wheel low and it is not in any gear.
I turn the switch and I cannot put in 4 HI or 4 LOW.
I have brought it to a mechanic he has checked out both actuators and said they have functioning properly. He is telling me that it is the ECM. Is this possible??

 

It's possible the 4wd ECU is bad but very unlikely, it's much more likely a wiring problem or issue with one of the limit switches in the 4wd actuators.
The best first step in diagnosing the 2nd gen 4wd system is checking the limit switch voltages at the 4wd ECU, see the thread below for details.
If you post your results we can see where we need to go.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/