4wd and transmission help

[Brian 162]

Hi all
I have an 06 Z71 Tahoe. While driving back from Charlotte last weekend the service 4wd message came on every time I started vehicle.
One time 4 Hi was engaged when I started vehicle. I put transmission in neutral pressed the 2wd. button, I heard a massive clunk but I was in 2 wheel drive.
I made it home.
The next day I tried reverse and nothing happened. Drive was fine.
I went to my mechanic and told him the whole story. With the mechanic now reverse works. The mechanic thinks I'm nuts.
He's had the truck for 3 days and everything is fine.
He can't scan a code because the fuse was blown for the obd2 so there aren't any saved codes.
Any advice would help.

Thanks in advance

[speeder]

Fix the OBD2 and drive it until it throws a code. Or doesn't. Do maintanence on TC if needed, (change oil).

[yetibone]

hearing a "wizz-clunk" is not unexpected when the TC shift motor rotates to change modes in the transfer case.

To fix the OBDII e-com problem, just replace the cigarette lighter fuse in the power distribution box under the hood. The orange wire at the OBD data port is the power wire, fed by the same circuit as the lighter.

Sounds like the shift motor might have been between AWD/4WD, and 2WD.

EDIT: You might need to find somebody with a Tech2 scan tool to access trouble codes for the automatic transfer case.

[vash]

anybody else miss the 4wd lever we had back in the day?

i miss it badly. even the manual hubs

[speeder]

Originally Posted by vash

anybody else miss the 4wd lever we had back in the day?

i miss it badly. even the manual hubs

I still have both in my truck.

[sixbanger]

I've got a 2000 s10 that does the same thing
It seems it shifts to 4x4 all by itself. And all the lights come on and
it feels like it is binding some where.Then it will fix it's self and not do it for months. It
seems to do it more in cold weather.

[yetibone]

Originally Posted by Brian 162

He can't scan a code because the fuse was blown for the obd2 so there aren't any saved codes.

Trouble codes will still be saved in the ATCCM and PCM history, even if the fuse to the lighter/OBD port was blown. That fuse has no bearing on the controllers' memories. It only provides power to the OBD port for the scan tool, indignant spouse's tracking device, or the insurance co. tattle-tale dongle to function.

[Brian 162]

Originally Posted by yetibone

Trouble codes will still be saved in the ATCCM and PCM history, even if the fuse to the lighter/OBD port was blown. That fuse has no bearing on the controllers' memories. It only provides power to the OBD port for the scan tool, indignant spouse's tracking device, or the insurance co. tattle-tale dongle to function.

Thanks for the advice. I'll pass the info along.

[Brian 162]

Originally Posted by speeder

Fix the OBD2 and drive it until it throws a code. Or doesn't. Do maintanence on TC if needed, (change oil).

I can wait until it throws a code. It's when I lost reverse and then an hour later reverse works is what I can't figure out.

[speeder]

Reverse shouldn't have anything to do w transfer case but then I admit I don't know what's going on over there.

[pen15]

Have your mechanic recheck codes in the TCCM. Will most likely find c0327 encoder motor sensor failure. The transfer case shift motor position sensor has lost track of where it is and tries to shift to where it was originally but ends up in a random spot between gears because the position sensor has failed. You can replace just the sensor but it is not a simple diy job. It has to be timed internally. Easier but more expensive to replace the entire encoder/shift motor. You will need to check the RPO codes found on the label in the glovebox to order the correct part. Should be NP1 or NP8

[Brian 162]

Originally Posted by speeder

Reverse shouldn't have anything to do w transfer case but then I admit I don't know what's going on over there.

Neither do I.

[Brian 162]

Originally Posted by pen15

Have your mechanic recheck codes in the TCCM. Will most likely find c0327 encoder motor sensor failure. The transfer case shift motor position sensor has lost track of where it is and tries to shift to where it was originally but ends up in a random spot between gears because the position sensor has failed. You can replace just the sensor but it is not a simple diy job. It has to be timed internally. Easier but more expensive to replace the entire encoder/shift motor. You will need to check the RPO codes found on the label in the glovebox to order the correct part. Should be NP1 or NP8

Will do thanks