1990 auto transmission help

[dccse3k]

Ok I have a weird problem.

There is a red plug from the auto transmission harness that plugs in next to the passenger side fuse box in the engine bay that when I leave it unplugged this happens:

D 2 1 all work fine except from what i can tell when i put it in 1 it is really in 2nd and when i go to 2 it shifts to 3rd. When i put it in drive it stays in third the whole time it seems.

But when i plug this red plug in when i put it in D 2 1 it stays in first the whole time and never shifts.

Does anyone have any ideas on what i could do other than hardwiring a switch so i can actually start out in 1st and not have the acceleration of a van?

also is the auto trans control unit inside the ECU? cause in the fsm it says its by the passenger kick panel but i can only see the ECU