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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1667
Experience:  GM Grand Master Technician 2007. 14 year experience.
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Have 2008 GMC Denali pick up with 50k miles. Range selector

Customer Question

Have 2008 GMC Denali pick up with 50k miles. Range selector shift feature quit working. No engine failure indications on control center. Had mechanic do computer diognotistic of tranny system and find no errors. Is there a fuse that may have blown or some switch that may have been engaged to turn off the range selector capability.
Thank, lee
Submitted: 9 months ago.
Category: GMC
Expert:  Greg Jensen replied 9 months ago.

HI lee, I'm Greg! So let me see if I hear you correctly. your truck is working normal but the digital read out on your intrusment panel cluster is no longer coming up or working at all?

Customer: replied 9 months ago.
No, the rang selector does not work. All I can do is put tranny through normal shift progression. (PRND). Will not go into any of the electronic/manual ranges (1-6).
Thanks, lee
Expert:  Greg Jensen replied 9 months ago.

Hello lee, Well I understand now what you are saying is your issue. I think a GMC Dealer may be able to track your issue down best. I ll tell you what I know form reviewing the system operation. There is no fuse that can be an issue. The Internal mode switch which is in the transmission. Tells the Transmission control module which Range is selected and then the TCM Tells the ECM and BCM what is desired and In turn the range seletion for gear adjustment with the switch is communicated through The BCM back to the other modules. as long as the trans cable adjustment is correct and the shifter is actually going into the Manual pos and then nothing is happening. I would speculate that the Internal mode switch has failed. The next possible failure could be the TCM. Though, I have replaced more Internal mode switches then TCM's on your type of transmission.