My 05 Yukon XL with 288k has got a 4wd issue. Just bought the truck about three months ago, and never tested the 4wd system prior to buying. The lights on the buttons illuminate, but shifting to neutral and attempting to shift into 4hi, 4lo, 4auto, or even 2wd yields no feedback. In fact, the buttons don't even show what the current configuration is. I am pretty sure it's in 2wd based off driving behavior but I could be wrong. Having looked at plenty of forum responses, everyone says that when this happens, they get a "service 4wd" messages. I have no messages, nothing that indicates the system is malfunctioning.
NEED HELP 4x4 Inactive
- Thread starter PSimm04
- Start date
Mooseman
Moderator
Is it a dummy light or a message on a 2005? I've got other messages for traction control and airbags that run across the message center, but nothing for 4wd.
My 4X4 Envoy occasionally shows a Service 4WD light. I believe it is simply a cheap 2WD/AWD/etc switch with contacts that are not gold-plated and oxidize over the miles. It may or may not be useful here. I simply switch it all over a few times around and it comes back to life. I hope this helps.
Mooseman
Moderator
Not sure if it's either. If something is wrong with the 4x4 system, it would do either a light and/or a message. If the TCCM is.offline, the BCM would throw the code.
I also have a 2005 Yukon with 4 button shift control.
Be aware that this control does NOT actually switch power to anything, it is only a low voltage (~5VDC) sensor input to the TCCM.
First thing I would try is remove the fuse that powers the TCCM for a minute or so to reset the TCCM.
Do you have access to any sort of scanner?
Be aware that this control does NOT actually switch power to anything, it is only a low voltage (~5VDC) sensor input to the TCCM.
First thing I would try is remove the fuse that powers the TCCM for a minute or so to reset the TCCM.
Do you have access to any sort of scanner?
Eric "O" from South Main Auto (SMA) gives us an excellent Classroom White Board Break Down and Under The Vehicle Diagnostic Approach on many of the issues involved with diagnosing GM 4WD TCCM Issues in this interesting and worthwhile Video:
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I'll give it a look after work. I wouldn't be suprised if there was corrosion somewhere in there as the salt air in Bahrain wreaks havoc on electrical systems.
I've got half a mind to replace all the button clusters on the dash since they've been getting cooked in Middle East heat for the past decade. I'll yank the fuse after work and pull the negative battery cable and let the computer do a reset. Ideally I'll get the truck to the shop this weekend and let them do a diagnostic on it to see if it throws codes that aren't showing up in the message block. More to follow.
Unrelated to your 4WD but since I have a same year Yukon I thought I would ask... what engine do you have?
That's what I have also. This is unrelated to your acceleration issue but are you aware of, and have you checked to see if you have the Castech 706 heads? Since you recently acquired this vehicle you may want to get familiar with this issue.
Checked the fuses a couple days ago. Unfortunately they were all good. I ordered the button cluster to see if maybe that's the problem.
I checked a couple days ago. It's not the original engine, and it had 832, or something like that. Not 702.
Alright, I really don't know what's the deal with this thing. I just installed the new selector button cluster. It gets power. There's no corrosion on the wires. The fuses are good. No codes (only O2 sensor code) for 4wd. No warning light/message. I have no clue. Any further ideas?
Not sure if this is conflicting info. Do you mean to say the backlights work but the mode indicator lights do not work? Or the mode indicator lights work but show no change when trying to shift modes??
Just now I checked my own 2005 Yukon. My Tech 2 will perform a lamp test and that does indicate and activate a "service 4WD" lamp. That lamp is an image of driveshafts, differentials, and 4 wheels with the front 2 at an angle.
However,,, when I manually send a functionally addressed message to turn on the "service 4WD" lamp the "lamp" does not light but instead I get the "Service 4WD" message on the DIC.
Also, this "Service 4WD" lamp does NOT turn on during the key-on bulb test. Only during a scantool or manually initiated bulb check do I see this lamp iluminate.
Did you specifically REMOVE the "ATC" fuse for about a minute or so to reset the TCCM?
Do you have any sort of OBD2 adapter or reader etc.?
The codes from the TCCM are required here.
So the backlights work on the button cluster. But there is not a light that illuminates for the drive mode the vehicle is in. Usually I think the orange LED lights up next to the drive mode. No matter which one you press when in neutral, no mode lights show up.
The lamp isn't illuminated, and there is no message in DIC for service 4wd.
I have not removed the ATC fuse. Do I also need to disconnect the negative battery cable as well?
I do not have my own reader, but the shop that scanned codes last week said the only code that popped was for the O2 sensors.
Pulling out the ATC fuse (#8) for a minute or two should reset the TCCM. This might allow the TCCM to work again for a while until the issue pops up again. But the TCCM might still see the same fault right away and again shut down the system. It is worth a try to see what happens.
No need to disconnect the battery at all. Pulling the ATC fuse will remove all power from the TCCM.
If the service shop you went to just did the "normal" scan for codes their tool might not even look for TCCM codes. Unless the tool knows that network address for the TCCM it won't get the 4wd codes. Some do, some don't.