02 Silverado HD - 4x4 Button Not Working

[Ol'Jim]

Just in time for the first big snowstorm of the Winter...
The transfer case switch panel (on dash) is acting like there is no power to it. The amber LED that indicates which range is selected is no longer lit. In past, it would do this once a year or so, usually when driving on really rough roads, and Dash message would say "Service 4WD". But it would go back to normal in a few miles or at next restart. This time, no message. It makes no noises.
Checked fuse box, not sure what fuse would cover this, nothing marked XFER Case, TC, or anything I would guess at. Could not find any blown fuses, I re-seated all relays, etc.
Climbed under truck, checked all connectors at TC, nothing evident there. Guess I'm glad it is stuck in 2WD, but it's looking like I may need 4x4 tonight/tomorrow. (Forecast = 8-14" of snow tonight).
Any ideas? Also, previous threads indicate it may be the switch panel, but I don't know how to remove the panel, to see if it's a connector issue back there, or to replace the unit. How do I access/remove the switch panel? Thanks, -Jim.

[j cAT]

Originally Posted by Ol'Jim

Just in time for the first big snowstorm of the Winter...
The transfer case switch panel (on dash) is acting like there is no power to it. The amber LED that indicates which range is selected is no longer lit. In past, it would do this once a year or so, usually when driving on really rough roads, and Dash message would say "Service 4WD". But it would go back to normal in a few miles or at next restart. This time, no message. It makes no noises.
Checked fuse box, not sure what fuse would cover this, nothing marked XFER Case, TC, or anything I would guess at. Could not find any blown fuses, I re-seated all relays, etc.
Climbed under truck, checked all connectors at TC, nothing evident there. Guess I'm glad it is stuck in 2WD, but it's looking like I may need 4x4 tonight/tomorrow. (Forecast = 8-14" of snow tonight).
Any ideas? Also, previous threads indicate it may be the switch panel, but I don't know how to remove the panel, to see if it's a connector issue back there, or to replace the unit. How do I access/remove the switch panel? Thanks, -Jim.

use a voltmeter and check all fuses. I doubt the switch would cause no lights on the transfercase select sw. also the switch issue with the bad solder joints will bring up service 4wd error lamp.

could be the 4wd controller mounted behind the switch being defective but I doubt it. no tools to remove this sw. pull the dash face off. best with the vehicle warmed up cold you may break plastic.

[Ol'Jim]

Originally Posted by j cAT

use a voltmeter and check all fuses. I doubt the switch would cause no lights on the transfercase select sw. also the switch issue with the bad solder joints will bring up service 4wd error lamp.

could be the 4wd controller mounted behind the switch being defective but I doubt it. no tools to remove this sw. pull the dash face off. best with the vehicle warmed up cold you may break plastic.

I need to correct, all the buttons are illuminated when the dash lights are on, but no LED indicator to show selected range.
I am told the dash face can be removed by putting gear selector down in 1st, then push downward on speedo cluster outer bezel. Is this correct?
(As you say, not wanting to break any plastic).
Thanks

[j cAT]

Originally Posted by Ol'Jim

I need to correct, all the buttons are illuminated when the dash lights are on, but no LED indicator to show selected range.
I am told the dash face can be removed by putting gear selector down in 1st, then push downward on speedo cluster outer bezel. Is this correct?
(As you say, not wanting to break any plastic).
Thanks

you might have to move the shift handle it does hinge back.

you pull toward you the dash panel then the switch will be accessable.

the speedo cluster clear panel you leave alone.you pull on the plastic that goes around those air vents a very good sized piece of plastic.

I doubt however this sw will be why its not working .

not downward. but to the rear of vehicle.

so with no led showing what the transfercase is in would be a fuse in most cases. especially if the service 4wd lt is not on. you select the 4wd position and hear nothing this indicates a fuse / power issue.

[Ol'Jim]

Thanks J cAT.
Any idea what fuse supplies the switch &/or XFER Case? I see one labeled ETC, (15A), another labeled ATC (20A). Both are good. Nothing else looks remotely like TC...

[j cAT]

Originally Posted by Ol'Jim

Thanks J cAT.
Any idea what fuse supplies the switch &/or XFER Case? I see one labeled ETC, (15A), another labeled ATC (20A). Both are good. Nothing else looks remotely like TC...

should be the ign 1 , 10amp, fuse , this feeds the atc logic and the select switch. this fuse also feeds instrument cluster, rear view mirror , bcm. so if it is blown wires under the dash must be shorting out.

pink wire .

[Ol'Jim]

Well,
Removed every fuse, from both panels, (underhood & LH side of dash). All are fine.
Removed switch assy, no evidence of cold solder joints, but one of the 2 micro-illumination bulbs is burned-out, can see open filament. (Which explains why 4LO & 4HI buttons are not lit at night). No way of knowing if the two transistors are good/bad. Reinstalled, no change. Searched all the large auto parts chain websites, virtually all show a unit that has a round "Auto 4WD" button on it. Mine does not, just 3 rectangular buttons, 2HI/4HI/4LO.
O'Reilly comes up with Dorman P/N 901-063, looks identical to mine. Even said "2 Connectors, 8-way & 4-way", which matches mine. Local store ordered it, had it in 4 hours, went to install it, and the smaller connector won't fit. My harness has 4 wires in a 6-position connector body, the new switch assy has a plastic ridge surrounding the connector pins, which is only large enough to accept a 4-pin connector. Looking at pics of every replacement part, back view, they all seem the same. Please don't tell me my truck is an early-production one with a non-standard connector... Sigh.
Because we got more snow last night & this morning, I basically tossed $50 out the window, by modifying the new switch to accomodate my truck's 4-pin connector. Plugged it in, and still no 4WD, or LED indicator to show range selected. Now the part is non-returnable. Dorman's website lets you plug in all your vehicle info, and it says the same P/N "fits your vehicle exactly"! Not so. GMPartsDirect says my OEM P/N is no good, (15067877), called local Chevy dealer today, gave him same P/N, my vehicle info, and credit card #, he said he will have the part tomorrow morning. What to do if it doesn't fit? Why the heck don't GM & all other car Mfrs put their damn parts catalogs online? (WITH pictures!!). Why are there 5 different versions of this switch, and ALL have same freaking problems? For 10 years? Shit shouldn't be so darn difficult, (sigh). Feels like my 3rd Monday this week, and it's only Tuesday.
I sure miss cars of the 60's & 70's...
My OEM TRW/GM Switch Assy:

[j cAT]

with a meter see if you have voltage at the ign 1 fuse.

see if you have voltage at the drivetrain select sw.

I guess you have the non auto 4wd, just the locked 4wd.

check the transfercase drive train computer box behind the select sw for the pink wire to have 12 volts. 8 volts should be to/on the select switch.

[Ol'Jim]

j_cAT, the new GM part fit correctly, (15067877 was superseded by P/N 19168769).
Picked up GM replacement switch assy today, has correct connector configuration for my truck. Popped it in, and I now have illumination of all buttons, but still no ability to select 4-HI or 4-LO range. Still no LED to indicate selected range. As you say, it appears to be a power/supply issue. No fuses are blown, and everything else works on the truck, so unless there is a dedicated fuse for this switch assy, I am thinking it may be an open circuit? There are 2 pink wires to the 8-pin connector at the assy - Pins B & G, (second from end on both ends). Would one of these supply the switch? I don't see any controller behind that switch, just some space and ductwork...
Thank you for taking the time to help me out with this.
Also, a tech told me there was a "reburn" on these trucks to address this same issue? He said to pull Fuse # 60, (Body Control Module), leave it out for a while, then reinstall it to clear the fault.
My fuses are not numbered. Can you tell me what the fuseblock designation for Fuse #60 is? (Nothing that resembles Body Control Module, that I can see). Is it underhood, or dash location? Is bringing my truck or ECM to a Chev dealer for reflash an option? Sorry to ramble, just thinking out loud here. Thanks. -Jim.

[j cAT]

the ignition fuse #1 is what should feed this circuit. this is in the under hood fuse box.
its late now so tomorrow I will look up the connector pins to the switch so you can check for voltage. also on my 2000 sil. the controller for the transfercase is behind the sw. I'll recheck that out also. the select sw lamps are from the transfercase controller which is a regulated 8 vdc.


under the fuse box rodents do make nests. they chew on the wires . they got me last year. this year no rodents I killed them all. rat traps and poison. no rodents and is very clean around my home. no damage to many things they got into in the past.

[j cAT]

the 12 volts from IGN fuse 1 goes to the select switch by way of the pink wire . with no auto button no sure if connector c2 G is the correct pin.

inside this transfercase select sw is an amplifier/electronic device. this is on the feed side of these led lamps. your lamps not lite. so if you do have a new switch and 12 volts going to it then the transfercase control module may be bad or wires to ground etc as this would be the device the makes the ground connection which will then cause the led to light.

[j cAT]

the 10 amp ignition 1 fuse is in the cab driverside of dash far side. open driver door and the fuse cover is on the side of dash.

the transfercase control module is behind the dash cover under the steering wheel.

[Ol'Jim]

Well, j_cAT - Thank you for the detailed information and advice. I was able to get a wiring diagram for the 4WD control system, and between that and your advice, I chased the power and ground circuits from switch, to Transfer Case Control Module. The TCCM Power Connector (4 wires) provides a ground reference at Pin C, which was unstable/flaky. Removed connector, cleaned contacts, reseated it, and problem is solved. Now have full 4x4 function. Thank you again, Sir. You are appreciated!

[j cAT]

Originally Posted by Ol'Jim

Well, j_cAT - Thank you for the detailed information and advice. I was able to get a wiring diagram for the 4WD control system, and between that and your advice, I chased the power and ground circuits from switch, to Transfer Case Control Module. The TCCM Power Connector (4 wires) provides a ground reference at Pin C, which was unstable/flaky. Removed connector, cleaned contacts, reseated it, and problem is solved. Now have full 4x4 function. Thank you again, Sir. You are appreciated!

well you saved a good amount of money with your troubleshooting this down to a bad connector pin. it does happen that ,sometimes these connectors inside the vehicle do get corroded. if a better plating material was used probably not.

tracing down an intermittent ground is difficult.

these type forums are a great tool to get answers on vehicle repairs .
good luck .