4x4 selector going to N - selection not working.

[nimrod.sixty9]

Symptom is that on startup the 4x4 selector is in N. Selecting any other mode, that modes light will flash for a few, then go back to N.
So I had this issue once before. Found a thread that mentioned that sometimes the communication fails to reach the modulator on startup. Fix was to remove the fuse momentarily. Of course this worked. Tho recently this is happening much more often, and without the need to pull the fuse, as by the time I start up next it is good to go.
My question is, is a component about to fail, and if so, what do I replace?

 

[Fless]

Best guess is that the encoder motor on the transfer case bit it. However, people throw switches at them first, since it costs less. TRW is OE and I get mine at the UPull. If you want troubleshooting info on the switch, see this thread: https://www.tahoeyukonforum.com/threads/03-4x4-issues.112093/
[EDIT: updated link to the atraonline article linked in that thread: https://atracom.blob.core.windows.net/gears/2006/2006-08/2006_08_08.pdf]


Removing the switch and ohming the switch modes can tell you if the switch is good or not. Several of us have found that disassembling the switch and reflowing the solder on the connector pins can fix a problem switch.

When you first turn the ignition key to "on" and the dash lights go through the self-test, do the mode lights on the 4x4 switch cycle through? (Auto, 2HI, 4HI, etc.)?

A Tech 2 would tell you what mode is being commanded vs. what mode is actually engaged. That's how I diagnosed my bad encoder motor.

 

[swathdiver]

A Tech 2 would tell you what mode is being commanded vs. what mode is actually engaged. That's how I diagnosed my bad encoder motor.

I gotta get out to his place again and help him check that out. My Tech-2 was mis-behaving last time and would not work on the 800s. I bought a new card and cable and it worked for a while but was acting up again on Friday night. Too busy to check it out, will run some tests on Tuesday when I'm off. You home by chance on Wednesday, Okeechobee Steve? If it works I can come out there and help you with the fleet. Don't make any plans though until I'm sure it'll work. I'll text ya too.

 

[Fless]

Nice to see a TYFer helping out another!

@******.sixty9 you should also clean and retighten the two grounds that are outside of the frame on the body, under where the driver's feet would be. They're right behind the LF wheel. One of those is for the 4x4, but I'm not sure if it's only for the front diff actuator or helps ground other parts of the system. One of mine had stripped threads in the body so I put a bolt and nut on that one.

 

[nimrod.sixty9]

Thanks for the info guys. I should note that all other times the 4x4 works perfectly fine, so the encoder motor does indeed work. Now it is to the point that the issue hasn't come back once since posting this. My guess is Tech 2 would show all is well considering how inconsistent it is.

I definitely need to check those grounds. Might explain the whining noise I always get from my speakers.
It is driving me mad.

James, sorry I just now seen your reply. I should be available anytime over the weekend, or tomorrow evening after work.

 

[swathdiver]

Thanks for the info guys. I should note that all other times the 4x4 works perfectly fine, so the encoder motor does indeed work. Now it is to the point that the issue hasn't come back once since posting this. My guess is Tech 2 would show all is well considering how inconsistent it is.

I definitely need to check those grounds. Might explain the whining noise I always get from my speakers.
It is driving me mad.

James, sorry I just now seen your reply. I should be available anytime over the weekend, or tomorrow evening after work.

Steve, I can't get the Tech-2 to talk to my Montana. I've swapped cables, adapters and moved the cards to different slots, just spent 30 minutes trying different configurations. The only thing I haven't bought another of is the VCI module and the Tech-2 itself. It powers up, just can't communicate after you build the vehicle.

As we were getting underway last Friday, the thing acted up again but this time with the Yukon. I swapped out the new cable for the old and it worked fine after that. New things can be or go bad so I'll have to do a cable test tonight after work.

 

[nimrod.sixty9]

Steve, I can't get the Tech-2 to talk to my Montana. I've swapped cables, adapters and moved the cards to different slots, just spent 30 minutes trying different configurations. The only thing I haven't bought another of is the VCI module and the Tech-2 itself. It powers up, just can't communicate after you build the vehicle.

As we were getting underway last Friday, the thing acted up again but this time with the Yukon. I swapped out the new cable for the old and it worked fine after that. New things can be or go bad so I'll have to do a cable test tonight after work.

Any luck?

 

[swathdiver]

Any luck?

The new cable worked fine on my truck but not the Montana again. I need more time to run a full battery of tests again which I'll try to do this afternoon after work. I'm beginning to suspect the VCI module, which I think my truck only uses as a pass thru device since it uses the CANdi.

 

[nimrod.sixty9]

The new cable worked fine on my truck but not the Montana again. I need more time to run a full battery of tests again which I'll try to do this afternoon after work. I'm beginning to suspect the VCI module, which I think my truck only uses as a pass thru device since it uses the CANdi.

Talking Greek to my buddy lol. Just going to have to take your word for it