I have a 2001 Blazer 4X4, automatic transmission and transfer case, 6 cylinder engine.
Truck is in limp mode. My pocket scanner pulled codes of P0740,0753,0758,0785 and 1860. All transmission related codes. Checked all my fuses, all good. No power at transmission pin E. Checked the ignition switch, seems to working as it should for start and run, except the white wire has no power when key is off. Which, if I read the anatomy of an ignition switch right, it should have.

I made a jumper wire from a wire that's always hot to the white wire, thinking that maybe that's my problem. all that did was activate my door locks and made the battery light stay on when the key was off and engine not running. So needless to say, that wasn't it. Ignition switch is good, acting as it should.
I'm thinking the white wire gets pulsed with power to unlock the doors when vehicle is shut down and then loses power when the key is turned to lock. And no power at transmission pin E.

So what to do now???

Looking around under the hood I noticed i had not tightened the upper connector on the PCM all the way. I remember I had to remove it and the radiator overflow bottle in order to gain access to the blower motor when I replaced it about 6 weeks ago.(BTW, who's big idea was it to cover the outer HVAC box with plastic you need to cut away in order to do any type of service work??)
I disconnected the battery, removed the connector to make sure it was good inside, it looked good, clean, no dirt or ash residue from possible arcing, re attached it made sure I tightened the screw all the way, connected the battery and now at my wits end, went for a test ride. Transmission shifted like it should. Went for 5 more miles, starting and stopping, no problem, no SES light. All is good now, right?
WRONG. This morning the SES light came back, the codes reappeared, limp mode agian. No power at pin E.

I don't have a super scanner to command the transmission solenoids, but I do have a friend with one. Before I bother him, does any one have any other ideas? Just seems strange it would work after I tightened the PCM connector, and then this morning it doesn't.

Any help would be appreciated. And thank you in advance.