4WD help?

[huntn2]

I am mechanically challenged so seeking knowledge from my to brothers. My '15 Sierra will go into and engage in 4 low but will not engage 4high. This happened before about 2 months ago and it was fixed at the dealer under warranty. It will be going back in, but I am interested in knowing what the hell this could be. It is manual shift on the floor for reference.

Thoughts?

 

[Beentown]

Speed sensor is my guess. It needs a correctly functioning speed sensor to be able to go into 4x4.

 

["J"]

Speed sensor is my guess. It needs a correctly functioning speed sensor to be able to go into 4x4.

But if it'll go into low lock? wouldn't that use the speed sensor as well?
Ryan, what'd they change the last time?

 

[Beentown]

Mine will go into low hut not high with a bad speed sensor. I would think it has to do with the "shift on the fly" which can't be done going into low.

 

["J"]

Mine will go into low hut not high with a bad speed sensor. I would think it has to do with the "shift on the fly" which can't be done going into low.

Gotcha... Never had any issues with any of my 4X4's with that at least..... Heard some complaints about GM and the module they used to engage disengage the transfer case.....

 

[Beentown]

I am sure you have forgotten more than I'll know. Just had a similar issue with a previous z71.

 

[jagermeister]

No experience with this but Beener's post seems very logical. Hopefully you get it figured out. Let us know what the dealer says.