NSBU switch on 2009 Allison 1000?

[Cf5757]

My truck went into limp mode "shift inhibited . . ." Code p708. Cleared code and tranny shifts hard or goes back into mode and can be reset by shift to N turn key and go until the tranny speed slows down and p708 all over.

Having read several posts about this code, I went and picked up a new NSBU switch at the local Allison dealer. Got under the truck to change switches and there is not one where all explanations said to expect it!

Does the 2009 Allison 1000 not have a NSBU? There are mount up holes,beside the linkage. Any insight appreciated.

 

[Mike L.]

My truck went into limp mode "shift inhibited . . ." Code p708. Cleared code and tranny shifts hard or goes back into mode and can be reset by shift to N turn key and go until the tranny speed slows down and p708 all over.

Having read several posts about this code, I went and picked up a new NSBU switch at the local Allison dealer. Got under the truck to change switches and there is not one where all explanations said to expect it!

Does the 2009 Allison 1000 not have a NSBU? There are mount up holes,beside the linkage. Any insight appreciated.

You are looking for an internal mode switch which is inside the pan next to the linkage. That may be your problem or it could also be a bad TCM.

 

[Cf5757]

Best to just replace them both or is there a way to isolate which is the problem?

 

[Mike L.]

Best to just replace them both or is there a way to isolate which is the problem?

Throwing money at it isn't a good idea.
You'll need a DVOM, Tech 2 would help alot, a wiring diagram, and a diagnostic tree to follow.
Your problem is somewhere in between the TCM and the internal mode switch.

 

[Cf5757]

Thanks for the insight. I will give a go at tracing it down

 

[Cf5757]

Sorry I no longer live in OC. This would be at your shop so fast!

 

[TTLMM]

Did you ever figure it out

Sent from my SM-G930V using Tapatalk

 

[Hambone]

Can’t find anything in search so this is the closet thread to what I need lol...
Do I need to do a fast learn after replacing the Mode switch in a 06 6speed?
And if so is it only tech 2 or will resetting the taps with efi live work?

 

[Mike L.]

No need to reset anything. Very rare to have a mode switch go bad.

 

[Hambone]

10-4 thanks Mike
Yea that’s what I’ve gathered from lots of research but everything was pointing to it so I’m hoping it fixes the problem otherwise I’ll need professional help lol
This is truck has done some weird things ever since the day we got it 14 years ago
Electric gremlins and the works

 

[Hambone]

For future reference
P0708 was only code set
All wires were good from tcm/mode Switch
Cleared codes when cold and would be fine until warm then PSND indicator would go out
And limp mode in third
Fluid wasn’t burnt
But serviced anyways because it was like 100k
I’m sure there is a test that can be done with a tech 2 but I don’t have one so I rolled the dice and won:thumb: