Unhook the battery. Pull on the wires at the rear of the connector one at a time. It is not uncommon for the pins to back out of the connector. May be your issue it may not, but it is common enough it is worth a look. Most times all you have to do is push the wire and pin back into the connector, sometimes you have to force a knife point into the tiny locking tab to pry it open a little so the pin locks into the connector.
Three power wires to the TCU, one comes from the ignition (yellow wire) through the inline fuse in the harness behind the TCU and is what switches the TCU on. Another (main power) is red and comes from a fusible link. These are the two most likely to cause you issues.
The third comes from the "TRANS" fuse in your fuse block through two wires coming from the trans selector switch (neutral safety switch) light blue with a stripe and grey with a stripe. This tells the TCU which position the shifter is in and one of these two wires only has power in either 1-2 or the other has power in Drive.
Check the ground at the dipstick brace, you may even have to ohm the ground wire from the TCU (connector) to the chassis just to make sure you have a good ground.
