Allison 5sp: 03 LB7 Intermintent Issues

[LBZ1991]

I've got an 03 lb7 that is perfectly fine one minute then gives me problems the next. Issues I'm having are when I start the truck the gear selector indicator light doesn't come on. When I put it in gear the truck limps to 3rd and the Speedo doesn't work, which as far as I know is causing the trans not to shift. Lastly when I hook up my solus it will connect to everything but the trans.. If I leave the truck sit and go start it again everything will be just fine and I connect the scanner and there are no codes. Hopefully all that makes sense and any help or ideas are appreciated.

 

[LBZ1991]

Anyone ever have similar issue? I've searched about everything I could find

 

[Mike L.]

Need codes.

 

[LBZ1991]

Only code I can pull is u1000. Scanner won't connect to the trans to pull any specific trans codes.

 

[DAVe3283]

It sounds like the transmission computer isn't getting power every time. When the TCM is unplugged/unpowered, it will behave like you describe 3rd and Reverse only.

I would personally look at replacing the ignition switch, they can go out and stop powering the things they are supposed to. But getting a better scanner and getting codes is the right way to do it.

 

[Mike L.]

Time to find a tech 2 and someone who knows how to use it.