1999 Buick Century transmission electrical problem

[Herb1949]

My 99 Century, 3.1engine has a 4T60E transmission. It has 145,000 miles on it.
I bought the car with a little over 80,000 miles, changed the trans filter at about 90,000. The car and transmission have worked great.
Last weekend I changed the trans filter and the fluid was a little burnt so I took it in and had a complete fluid change done.

On monday the trans quit shifting correctly. T-shooting, the trans fuse is blown. Replaced fuse and it blew again as soon as I started to drive it.

Pulled the codes, P0758, P0754, P0740 and P1870.

Reading, on here and on other sites I found some electrical checks to do.

As I understand it the solenoids all have power all the time through pin e of the connector and the PCM provides a ground to change the gears. Started to do the checks, with the transmission connector disconnected. Discovered that pin e has about 7 ohms to the case and the shift solenoids have 23-24 ohms to the case, the same as I found when reading through them. This seems wrong because the PCM is supposed to provide the ground.

Questions are, has anyone ever t-shot the electrical before? Is this normal? Could I have one of the power wires shorted to ground inside the case? Are there any t-shooting steps for the electrical system on the transmission? Does anyone have a book on the 4T60E that they want to sell, or would be willing to make copies of pages and mail to me? What about a real wiring diagram of the wiring in the transmission? According to the diagrams I have, there are only 5 wires going in and my plug has 6. The plug is not marked for the pin locations and I had to find the input pin by a continuity check from the fuse to the connector.

I found a place where I can get the internal wiring harness and all of the solenoids for about $130.

I am sure that I can fix this but don't want to tear the whole left side of the car apart until I am pretty sure of what is wrong and have parts to put it back together.