Transmission setting changes between starts- I have a 2003 Yukon XL since new- the transmission settings change between starts - 2wh to 4L to All whee

[MrMike]

I have 2003 Yukon XL since new- now between starts it will change transmission settings- 2w to 4L to All wheel to neutral-
I have changed the ecm unit and the switch on the dash - it has been reprogrammed - no performance issues- just trying to figure it out

 

[Fless]

It doesn't sound like the transmission, but the transfer case. Post up a pic of your 4WD dash switch, please. It probably needs a transfer case encoder motor or the ring inside it.

 

[rockola1971]

I doubt its changing postions by itself. Its more likely just a position feedback signal errantly going through a dirty commutator in the Tcase encoder shift motor. The commutator can be replaced separately or you get a new one when you buy the whole encoder shift motor.

 

[MrMike]

 

[MrMike]

This is the dash switch recently replaced- also when the truck is turned off in 2H it will restart in 4L -I put it in natural and u hear the clank to change back to 2H - so it does change between starts- but it’s random which setting it will start in - unless in 4L just hitting the button gets it back in 2H- I don’t have a deep understanding of this system -

 

[Fless]

You need to get a good bidirectional scanner on it to see if the (2/4WD) commanded mode matches the actual mode. A Tech 2 or other advanced scanner that can read those data.

Your truck has the NVG246 2-speed transfer case. Likely the cause will be the encoder motor ("transfer case motor" on RockAuto) or specifically the internal "Transfer Case Range Position Sensor" as @rockola1971 noted.

A few years back my switch commands didn't match the actual modes, and I ended up putting a new encoder motor on it. I could have torn it apart and replaced just the internal range position sensor, but didn't.

 

[rockola1971]

You need to get a good bidirectional scanner on it to see if the (2/4WD) commanded mode matches the actual mode. A Tech 2 or other advanced scanner that can read those data.

Your truck has the NVG246 2-speed transfer case. Likely the cause will be the encoder motor ("transfer case motor" on RockAuto) or specifically the internal "Transfer Case Range Position Sensor" as @rockola1971 noted.

A few years back my switch commands didn't match the actual modes, and I ended up putting a new encoder motor on it. I could have torn it apart and replaced just the internal range position sensor, but didn't.

Its actually a 246E (E=Enhanced)