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2002 chevy trailblazer_lt
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Discussion Starter · #1 · (Edited)
Alright, im no noob to the forums and have ready dozens of threads on bad slector switches ETC, i think mines finally gone bad but it cant hurt to make a thread and get others opinions, so here it goes.

Tonight i got in my truck, started it and noticed that only my 4WD Selector Switches Backlighting was working, the little orange indicator DOT that lets you know what mode your in was NOT lit up, there was only backlighting no dot whatsoever

i messed with the switch a little clicking it in different positions and no dot whatsoever would come on. I turned the vehicle off and clicked the switch about dozens of times as other threads have stated to try and clean the switches contacts off and still nothing.

NO DASH LIGHTS whatsoever, The Service 4wd Light is NOT on, the truck is stuck in 2wd mode as i rolled my window down and switched through the various positions and heard no actuator noises whatsoever so the switch is definately not functional, there is no indicator dot whatsoever in any position, yet NO dash light are illuminated, it simply does not work

I forgot to mention ive also had other issues recently like i will hear a funny noise and look over and my truck will be in 4wd for no reason even though the switch is selected in the 2wd Position so ide have to click it off 2wd and back onto 2wd to get it to switch back to where it should be, another problem thats common with switches going out ive heard, also the 4wd fuse in the rear box is NOT blown

ideas?
 

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2003 gmc envoy_slt
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Have you checked the fuses? I think it's #48 in the fuse box under the back seat.
 

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Discussion Starter · #3 · (Edited)
No i havnt, ide be more scared of a blown fuse then having to buy a new switch, considering a new switch is $12 dollers shipped on ebay and if a fuse is blown you have to wonder what caused that to happen

I forgot to mention ive also had other issues recently like i will hear a funny noise and look over and my truck will be in 4wd for no reason even though the switch is selected in the 2wd Position so ide have to click it off 2wd and back onto 2wd to get it to switch back to where it should be, another problem thats common with switches going out ive heard
 

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Discussion Starter · #4 ·
Just checked the 4wd fuse in the rear box, its not blown
 

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2004 gmc
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Definitely try the switch first, especially with its history. I like your philosophy of wondering about a blown fuse. SO MANY idiots just slap in a bigger one trying to FORCE the circuit to fix itself. :x

I'm on the road at the moment, so Internet access is limited. Good luck, and I'm sure you'll post the result.
 

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Discussion Starter · #6 ·
Thanks, i picked up a new switch on ebay for $12 dollers shipped lol
 

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Discussion Starter · #7 · (Edited)
Put in the new switch and didnt change anything, still have no indicator light on the switch, the 4wd fuse is not blown and there is no service 4wd light active on the dash, but 4wd is INOP

I even started the truck with the selector switch completely unplugged with nothing connected to the harness and the service 4wd light still did not come on

Bad 4wd Module?
 

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Discussion Starter · #8 ·
buump
 

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2004 chevy trailblazer_ls
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With the ignition in accessory mode try running the switches through the different positions. Are you hearing any movement of the actuators? If you are there is probably a wiring problem some where in the dash. If not then I would guess you do in fact have a bad fuse or relay.
 

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2002 gmc envoy_slt
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Reset the TCM by pulling the fuse under the hood, my lights went out on mine 2-3 years ago and that's what fixed it.....haven't had a problem since. Its either the #7 or #8 fuse in the box under the hood.....along the side of the box facing the engine.

GM actually has a TSB out dealing with the TCM not 'waking up' correctly and the first step if the Tech is unable to communicate is to pull the fuse, re-seat it after 30 seconds and try again. No light over the switch and a dash 4x4 light, usually means something with the TCM, this is the simplest of the trouble shooting items to try.
 

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Discussion Starter · #11 ·
There are no actuators when the key is ON but not started, nothing works in any position and the fuse is not blown.

Bad 4wd module?
 

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2004 gmc
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Some early modules were bad, and GM also updated the TCCM flash program. Try swapping with a local trailvoy if you can find one to support our next guess that it's the TCCM. You could poke around with a meter and make sure all the inputs to the TCCM are as expected, but that's tedious.
 

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Discussion Starter · #13 ·
the 4wd Module is located under the dashboard right around the steering wheel area correct? ill try to pull the underhood fuse and let you know what happens, the only one ive done is the 4WD Fuse in the rear fusebox i havent done anything with the engine fuse box
 

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Discussion Starter · #14 ·
I pulled the fuse as others have stated that's located in the engine bay, when I turn the car on the selector switch indicator lights now light up and then go out and the service 4wd light is now illuminated on the dash
 

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2002 gmc envoy_sle
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I just had a similar experience this morning. I got in and started it (actually the engine didn't start on the first crank, so I had to turn it over again) and all the indicator lights blinked as usual and then the 2wd light started blinking for about 5 seconds and then went out and wouldn't come back on with turning the switch back and forth. Tried restarting the truck and the same scenario occurred. I drove to work and shut the truck off (about a 20 minute ride), went inside to get morning java and came back out and switch was working fine when I restarted the engine. It makes me wonder if it is the TCM YLAB mentioned. I too have also had the problem of the switch changing into AWD while driving down the road.
 

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Discussion Starter · #16 ·
Im pretty sure the next step would now be finding someone with a Tech2 and trying to communicate with the 4wd module and if it can't communicate then the module is bad correct?

Im still not sweating about it as a new 4wd module is $50 dollers on Car-Part
 

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2004 gmc envoy_sle_xl
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So i am reading up on old news and thinking i may be having the same problem... does your story have a happy ending? What did you find out? Thanks.
 

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hello! I know this is 10 year year old thread but I figured I'd give it a shot...

I have 2004 Silverado with this same issue (No lights on selector and no service 4wd indicator). i checked to make sure fuses were not blown already. I followed ylab's advice and pulled the fuse under the hood for the tcm. i now have Service 4wd on the dash and the selector lights up when keyed on but it is still not working.

After poking around and getting the service light i gave up for the night. the next morning i still had the light on all the way to work (60 miles) after work i jumped in the truck to leave and noticed that the front end was binding like it was in 4WD! i got excited and played with the selector for about 5 minuets and could hear and feel that it was engaging and disengaging through Auto, 2HI, 4HI, and 4LO!

Confused and a little frustrated I proceeded to drive home stopping every one in a while to make sure it still worked. lol I pulled into the driveway and put the truck in park and the Service 4WD light blinked back on... after playing around with some stuff the service 4wd ligt shut off and the selector switch stopped lighting up when i keyed the truck on. I've since pulled the 30A TRAC fuse that is under the hood and plugged it back in and now only get the service 4wd light again..

Snow is apon us and definitely don't want to be caught 30 or 40 miles from home with no 4WD on sh!tty Roads!


Any Help would be greatly appreciated!!! Thanks in Advance!
 
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