Bad NSBU switch?....... need help ASAP!!!!

BlackCloud83

BlackCloud83

New member
Joined
Dec 23, 2012
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4
hey everyone. my 03 gmc duramax with the Allison trans is acting up . i was out plowing in the 6" of wet slush we got for 18 hours straight today .....now it wont go into gear every time. heres the symptoms below. correct me if im wrong but i think it is the NSBU ( neutral safety back up switch ) that has finally gone bad . i do know they have alot of issues with the o rings leaking.

- delayed gear change ( go from reverse to park and once in park the reverse beacon still gos for 5 seconds )
-PRNDL display is so weak i cant even see it ( and no its not dimmed )
-display has flashed " range selector inhibited " several times
-every 10 shifts or so i cant get it into gear even after cycling the shifter.
- trans fluid is at proper level, not burnt , good filter and shifts just like normal not in limp mode.

any imput would be greatly appreciated since this is my only work / personal truck at the moment aand i have hungry kids to feed !
 
He!! of a first post. Hook a scan tool to it to see what's happening.
 
Watch the nsbu voltage signal to see what its doing. Codes don't mean shlt.
 
Then you're stuck playing Russian roulette with expensive parts or getting a better scan tool.
 
id replace the switch if you find an allison dealer close to you there only 65$ everywhere else is 300+ just google allison dealer then your zip code
 
Question: is switch on trans black or tan? Black was the old style that had issues.
All those are symptoms point to a bad NSBU.
 
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