How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
Type Your Chevy Question Here...
GM Tech (Cam) is online now
A new question is answered every 9 seconds

2004 Silverado 2500, non HD, Autotrac t-case Not getting

Customer Question

2004 Silverado 2500, non HD, Autotrac t-case
Not getting power to the 4wd buttons on the dash. Replaced the dash buttons, replaced the 4wd actuator motor, still nothing
The truck would start off in 4wd low, on it's own, I could put it in neutral, shift to back to 2wd, and all was good.
One day it said service 4wd, and the buttons stopped working, that was a year ago.
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
The tcase is now in neutral, it's no longer in 2wd
Expert:  Greg Jensen replied 1 year ago.

Hello my name is***** are multiple service tsb's for differnt codes in these systems. Have you had it scanned at all yet by chance?

Customer: replied 1 year ago.
no I have not. I have HP tuners, but it does not show anything from it
Expert:  Greg Jensen replied 1 year ago.

It sounds to me Like the module may be the issue esp sense you already replaced the encoder motor and the switch assemble. you could try next to remove the fuse for the tccm, It is located In the underhood fuse block. remove it for a few mins then reinstall it to see if it will at least function again. there are several updates that gm has for your tccm for these type of issues, however, If you have code c0550 stored we know the module will need to be replaced. Also this module has to be programmed to your vehicle. So, it would require a dealership visit.

Expert:  Greg Jensen replied 1 year ago.

I looked I may be incoorect the fuse my be inside your I/P fuse block which is on the L/H side of your dash.

Expert:  Greg Jensen replied 1 year ago.

It should be labeled 4WD

Customer: replied 1 year ago.
I checked the 30amp fuse under the hood, marked as TREC, and its good.
There's no 4wd fuse on the drivers side fuse box in the cab
Customer: replied 1 year ago.
I now have a tech2 MDI and a Matco MaxMe scannersnothing for the TCCM has showed up anywhere
Expert:  Greg Jensen replied 1 year ago.

Did you try removing the TREC fuse and letting the module power down?

I looked at the schematic that should be the correct and only fuse and based on your saying that you have no comm with a tech2 for the tccm. You next can check the power and grounds to the module before replacement.

Customer: replied 1 year ago.
i have tried pulling the 4wd fuse under the hood and the TREC, and waiting 30sec and tried to read for codes, and there was no change.
I picked up a new harness, 15895628 and I'm going to try that next
Expert:  Greg Jensen replied 1 year ago.

It is sounding more and more like you have a bad module. you Might want to check for this issue as well.

Expert:  Greg Jensen replied 1 year ago.

we can prove if it needs a module pretty easily by just doing a few checks of your powers and grounds and data comm ckts at the tccm. if you have power and grd/ good conn on the data line. then you have a bad module and I have replaced alot of those modules.

Customer: replied 1 year ago.
well the new harness didn't make a difference.
I have a New TCCM, it's been plugged in before with no changes.
I now have a new dash switch, new actuator, new tcase harness . . . still nothing
If I plug in the new TCCM, still no power on the dash buttons.
The old TCCM had no evidence of water issues
Expert:  Greg Jensen replied 1 year ago.

Have you checked checked your powers and grounds at the tccm?

DO you need that schematic?

What op code is your system, you can find the op codes of the vehicle in the glove box on the white sticker. its either np1,np2,np3 or np8?

Customer: replied 1 year ago.
sir, I have checked the ground and power going to the TCCM. The ground and orange (always hot) are good.
I have the NP8I'm now wondering about the wake signal wire, where is it and is it a ground or hot wire. . . . ?I'm open to any and all suggestions that you might have.
Expert:  Greg Jensen replied 1 year ago.

Im in it to win it so WE will keep grinding on it. Go to the switch it self and check on connector 1 spot G should be a brown wire, check it for power with the ign on.

Customer: replied 1 year ago.
connector 1, post G - hot at ignition - it's good
Expert:  Greg Jensen replied 1 year ago.

locate splice pack 205. its hard to find but its under the l/s of the dash here is a pic.

then you can disconnect it and check the data line to the tccm.

You can see the tccm is also in conjunction with the ebcm, so you might want to make sure you have good comm with the ebcm and if you do that tells us the the data lines working from the splice pack back.

Expert:  Greg Jensen replied 1 year ago.

Here is this sch as well if you dont have it.

Customer: replied 1 year ago.
Im assuming that I'm testing them for continuity ?
Expert:  Greg Jensen replied 1 year ago.

yes, just trying to cover our basics