4l60e transmission not down shifting

[Mrrefrigeration]

2002 Silverado with 4.8. And a rebuilt 4l60e trans. It?s a restomod with painless wiring.

Transmission start out in first and goes to 2 and 3rd gear. Come to a stop and it?s stuck in 3rd gear won?t down shift to first. Restart truck and it starts in 1st gear again

You can command it in hp tuners and it goes through all the gears.

[blindsquirrel]

This is going to sound harsh, so I apologize. It's not just you, it's... society, a trend, whatever.

When someone shows up asking for help with a technical problem in a complex system, and the only info they're able to give is a story of what they think might be happening, and do not post the tune file that's being used when this problem occurs, and they do not post a log file showing the problem happening, it tells me that this person has not done even the most basic of work on their own to sort things out, like reading the important 'sticky' threads that tell you very very plainly: "If you want help post your tune file & log file."

[TransGo Robert]

Transmission start out in first and goes to 2 and 3rd gear. Come to a stop and it?s stuck in 3rd gear won?t down shift to first. Restart truck and it starts in 1st gear again

The computer is detecting that something is wrong so it puts it in failsafe 3rd gear only until you cycle the key. You need to scan it and see what DTC(s) it is setting.

[Alvin]

Check for a code after it gets stuck in 3rd gear

[Mrrefrigeration]

Thanks for the help. It was the harness manufacturer didn?t hook up the u terminal to transmission. All Works great