[Pillow]

Well the Burb is new to us... First snow of the season in VA... The wife parked the Burb at Dulles airport on Wednesday only to come home this afternoon to a winter wonderland!

So she takes off from the airport and hits the "4 Hi" button... Nothing!!! No lights on the buttons at all! I figured the "2 Hi" would be illuminated. No lights period. Push any button and nothing happens.

LUCKILY we put on new Revos which eat up snow like a champ! No rear locker either!

She came home no problem

But is there any tips on getting the Auto-trac back on track? Since there are no lights at all I suspect it may be a fuse???

Thank you so much for any input!

 

[runnwo]

The ealry auto tracks had bad push button switches. The solder joints cracked, If it is under warrenty they should replace it. Sometimes you can just hit the button housing and it will light up and work for a while. You can either replace the switches for like $80 takes 10 min or remove the switch and touch up the line of solder joints on the back. I had to look close but on my old truck almost every one was cracked.

 

[stacks04]

it could also be the transfer case control module. we've done a ton of them over the last couple of years. there mounted in the dash on the driver side. if you know someone that has access to a tech 2 (gm scan tool) the can run a simple light test to see if the scanner can light the bulbs. if not, the switch is probably bad.if yes them its the module.

 

[jeffster]

Both posts are right on. Had the same issues in my 2000 Silverado. Wasn't that much to fix, but happened at the most inconvenient time. Good luck!

 

[mikek996]

Both posts are right on. Had the same issues in my 2000 Silverado. Wasn't that much to fix, but happened at the most inconvenient time. Good luck!

those are 2 completly diffrent systems 99 burb is old body style 2000 silverado is neww style. there may be a way to flash code it i will look then post procedure if there is.

 

[mikek996]

since you said auto trac it must have the auto 4x4 4 buttons right? you need a tech 2 if it was push button non auto you could jump dlc to flash codes. chances are if you clear dtc it will work for a while again.

 

[Pillow]

Yes, it is the push-button 4x4 system. No floor shifter.

I checked it out a little bit today and found that it is #2 fuse (20 Amp). The fuse was blown. I replaced the fuse, cranked her up, watched the auto-track lights flash and then settle on "2 Hi", and then shifted out of Park.... Bam! Blew the fuse again.

Some wiring is the system must be bad... No clue what at this point.

Thanks for the great info! I am completely new to automatic transmission much less automatic differentials!

 

[mikek996]

no i know its push button but there is a 3 button and 4 button versions. 4 button adds the auto selection. ill do some checking on the fuse and get back to you. at least shorts like that are easier to find than the one that blows the fuse intermittantly. look at option codes in glove box tell me if you have np8 or np1

 

[mikek996]

i was looking at the schematic that fuse feeds the transfer case control module only. the fuse blew when shifting from park??? ordid it blow when shifting the t-case. if blew shifting from park I would look at all the wiring under the steering column. there is lots of places a wire could chaffe against metal. test it with a circuit breaker and not fuses you will blow too many fuses trying to find it at least the breaker will reset when cooled off. is this fuse under the dash or is it in the engine compartment? whichever it is follow the wiring harness see if you can see it rubbed anywhere. if you dont find any problem try unplugging the tccm and see if it blows could be a short in the module, not likely though.

 

[Pillow]

The option code is NP8.

The fuse box is inside the dash.

I will try and dig under the dash to find any frayed wires.

There are no SES codes currently.

Thank you very much!

 

[mikek996]

it should be an orange wire. it will most likely be rubbing in some metal bracket. if it pops shifting out of park concentrate around the column.

 

[Pillow]

Fixed!!!

This is classic... Either the PO or some bo bo mechanic did not properly route the electrical wires to the transfer case during some service. Needless to say the wires fell from above the tranny and down onto the front driveshaft! After some miles of rubbing it eventually chewed through the wires wrap and cut into a couple wires

After the autopsy I found that only two wires were hurt, luckily. One thick 12 guage black wire, which I suppose is ground for the transfer case. And one 16 guage white wire, which I have no idea what it does.

So some cursing and splicing later we now have a working Auto-Trac system! Also a few four letter words in re routing the wire loom to the correct path to avoid this happening in the future.

In the end I am happy it was not something under the dash, as working on the floor in a 31F garage is bad enough. Needless to say I was pretty frozen by the end of the project.

Thanks so much for the help guys!!! Much cheaper this way than going to the stealer