4 wheel + fog light LED not working

[akvanden]

The LED indicator light on my 4WD switch is not indicating what mode it's in. The switch works properly in the sense that it goes in and out of 4WD as it should, but the orange light on the switch itself is not. Figured it was the switch itself until this morning I notice the same was happening from my fog light switch. The fog lights would come on but then LED indicator showing them on would not (switching between high and low beam did nothing).

Any idea why both would not be working?

 

[The_Roadie]

You may have other lights also out on dash switches like the rear wiper control?

Dimmable dashboard lights are on one of two fused buses that are controlled by the BCM. In the rear fuse box, look for fuses marked "TBCx" and I think the dimmable lamps are fused by 2 and 3, or perhaps 3 and 4. Check all the "TBC" fuses for continuity and I think you'll find your culprit.

Why GM uselessly labeled them "TBC" (Truck Body Controller) instead of their function is beyond any of us. The designers were goofballs in many cases, and the technical writers were like monkeys trying to pound out Shakespeare.

 

[akvanden]

You may have other lights also out on dash switches like the rear wiper control?

Dimmable dashboard lights are on one of two fused buses that are controlled by the BCM. In the rear fuse box, look for fuses marked "TBCx" and I think the dimmable lamps are fused by 2 and 3, or perhaps 3 and 4. Check all the "TBC" fuses for continuity and I think you'll find your culprit.

Why GM uselessly labeled them "TBC" (Truck Body Controller) instead of their function is beyond any of us. The designers were goofballs in many cases, and the technical writers were like monkeys trying to pound out Shakespeare.

Does the rear wiper control have an orange light indicator? I'm not talking about the white back-lighting - that works fine, just the orange light that shows which 4x4 setting your in and if your fog lights are on or not. Irregardless, I'll try and check those fuses. Thanks.

 

[The_Roadie]

I don't have my schematics with me at the moment to tell you about the , but the 4WD control switch orange lights are on the dimmable lamp bus same as the white backlighting on many other switches. Another clue is if all four go on for a second when you turn on the ignition. That's the lamp test period. If they flash on, then the fuse is good and the TCCM is booting itself OK. Many 2002 vehicles fail to do this as they age.

Your fog light indicator failure may be something else.

 

[akvanden]

I don't have my schematics with me at the moment to tell you about the , but the 4WD control switch orange lights are on the dimmable lamp bus same as the white backlighting on many other switches. Another clue is if all four go on for a second when you turn on the ignition. That's the lamp test period. If they flash on, then the fuse is good and the TCCM is booting itself OK. Many 2002 vehicles fail to do this as they age.

Your fog light indicator failure may be something else.

You sir, were correct. TBC 5 was blown. I don't have any fuses with me at the moment, but that must be the culprit. Thanks!

 

[mrwitty_1]

I have also noticed that the fuse labeling actually has no clue as to what is protected by the fuse. My question, has anyone found a description as to what each fuse protects ?

 

[IllogicTC]

I have also noticed that the fuse labeling actually has no clue as to what is protected by the fuse. My question, has anyone found a description as to what each fuse protects ?

For the most part, the labeling is fairly accurate. There are a couple of scenarios where something minor is daisy-chained off a fuse for something else. When you have this much wiring in a vehicle it's bound to be designed that way sometimes.