autoshift will not go into any gears no error code, just flashes

I recall a solenoid on top of transmission could fail or be stubborn. Common to tap with hammer to engage.

 

just disconnect the negative battery cable for about 5 full minutes. reconnect, and see what happens. then make sure to check the tightness of all the battery cables as well.

 

Checking the grounds... Start at the battery box and work out on each cable, + and -. Chase them all, you are looking for corrosion, oxidation and bare copper. If you have bare copper on any of those cables and or grounds, you more than likely will have to replace that entire cable. Clean the connections as you go. On the grounds, you should have one going from the starter to the frame, fifth wheel to the frame, and possibly one from the transmission. Automatics are something I avoid, for the very reason you are here. Also, replace any related fuses, even if they look good, replace them. Same with any relays. See if you can get a wiring schematic of your particular truck model. I have an 08 ProStar and use the electrical schematics at least once a month to test and or diagnose issues.

 

I agree to check the wiring.

But did you try to reset the ECM for the transmission?
Start the truck and build up air till full. Shut down the truck and cycle the key 6 times on and off. Then leave it off and wait. It could take up to 20 minutes but at some point you should hear the transmission start to shift.

 

As stated above the grounds need to be traced down and cleaned their were 6 on my pete.

 

Their are I believe 6 sensors on the truck with 1.6 on the clock its time to change them
Its hard to tell but that computers may be getting water inside it when it rains.
Their should be a red service light on the shifter that will give you a blink code.
Has the truck ever been going along and feels like the key was quickly turned on and off ?
Google Eaton Auto shift 3d generation and read.
Where are you located ?

 

Have you released your brakes and tried putting it in gear or rolling the truck back a bit, sometimes they can get into a gear bind.