Truck doesn't go into gear

[Dennis.max]

I have a 2001 Chevy Duramax has the Allison trans. Wouldn't move the indicator on the dash would just flash so changed the nsbu switch and no difference, had the tcm flashed and reprogrammed and still nothing so I changed the ignition switch and the truck then went into gear but took a few seconds before it kicked in then went back to not moving and just flashing on the dash. Also if I unplug the 4 pin wire connector on the nsbu switch the truck will move but only in limp mode. Any help would be awesome this truck has had me spinning for awhile now

 

[Chevy1925]

Pull the codes and quit throwing parts at it hoping it will fix it

 

[Dennis.max]

The truck doesn't set any codes

 

[Burn Down]

What are you using to ck the codes with? Cheapo scan tools normally won't pull allison codes.

 

[Dennis.max]

Snap on Ethos, the check engine light doesn't even come on

 

[Dennis.max]

I can get the truck to move but once I do I can't go far and it will just quit moving and the gear selection flashes but truck won't move unless I cycle the key a few times

 

[Chevy1925]

You have codes, you just have an electrical issue going on that needs to be address. Start at the Tcm and follow the wiring back looking for frayed or cut wires.

Did you put the nsbu in as the instructions stated?

 

[Dennis.max]

Yes I did and checked all the wiring the dealership I took it to to get tcm flashed look over the wiring as well and didn't see any problems

 

[Blackmax123]

Start simple. Have you checked the oil level?

 

[Mike L.]

May be plugged sump filter.

 

[Dennis.max]

That's the internal filter right?

 

[KyleC4]

Yes. Pull codes or have someone with a tech II actually look at data when problem occurs

 

[Dennis.max]

I have