T680

The batteries are probably garbage, which will cause all kinds of random issues, because of the amount draw they’re placing on the alternator and robbing power from the other systems. Install fresh batteries and get the truck out on the road; not idling.

Modern trucks have a parasitic draw on the batteries, at all times. That slow draw discharging the batteries until they’re completely flat is what permanently kills them. Hook up a solar charger, if you’re going to leave the truck sit for long periods of time. It’s why fleet trucks have small panels atop their roof fairings.

 

You probably have stale DEF, so you'll have a DEF quality fault. The transmission fault is probably electric related. Dump the DEF and refill. Test the batteries. Check the alternator.

Someone more mechanical than me will chime in on which sensors should be cleaned or replaced.

 

What ducnut said.
Also when you do need to idle set the cruise control up to around 750 RPM.
If you have an automatic like the T680 I drive,, well that’s another issue. Those things are crap and the control stalk also has issues. It’s a cheap plastic piece of crap. Mine has been changed out three times last year.

 

Yup, stupid thing just had me broken down for a week. The mhc my company towed me to had to order the part and it was delayed to due weather. Not my first time either, and it strikes with no warning. Just when you go turn the key when you're ready to leave...nothing, and then you see the red gear of death on your dash.