yes depending on the code the transmission connector would be unplugged and with a scan tool testing the on and off ground controls from the computer to the transmission connector is done next and be sure the ground is good and the power to the connector
if there is a missing power or ground we go after that if there is a control wire when commanded on and off that is not triggering and on and off signal when commanded with the scan tool then that command wire or terminal at the connector OR the computer connector will be tested next and if the wire tests good and the terminal tension and terminal itself tests good then the computer would be replaced
if all the command wires and power and ground test good then the issue is the internal wiring harness inside the transmission bad which would be tested
if by chance that tests good then the issue is defective solenoids OR the valve body valves the solenoid controls are binding or sticking and debris in the channel plate behind the valve body would be checked next and basically will turn out to be a bad valve body or channel plate OR possibly a little bit deeper like a torque converter issue
BUT the next step is the problem cut in 1/2 :
is the problem a control problem = wiring or terminals or computer
is the issue inside the transmission = internal wiring harness , valve body ect...
that is how this problem is solved correctly