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2003 gmc envoy_sle
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Discussion Starter · #1 ·
Ok, just bought a 2003 Envoy two days ago. I noticed when at a light the lights on the selector went from 2wd to 4wd (without touching the switch). And i did hear and feel the transfer case change. i moved the switch to 4wd and back to 2wd and it went back to 2wd. Hope it does not go to 4lo when i'm rolling down the freeway!

The selector switch itself?

The other issue i have is when i tried to move the seat. the lights dim and the seat did not move. so i reved the engine and tried again, the seat moved with no problem.

Battery?
 

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2004 gmc
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26,181 Posts
Didn't hear of a recall, but the switches are cheap, even at the dealer, and they were redesigned for more reliability around 2005. You might try running it CW and CCW a hundred times to see if the contacts clean up by themselves. The system needs to be exercised every month or so anyway to make sure it will work when you need it.

On the seat issue, what's the voltage at the battery at idle. Measured with a real voltmeter, not the dashboard one. How old is the battery? You might have a dirty seat switch too. Run the seat back and forth a dozen times and see if it improves.
 

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2004 chevy trailblazer_lt_ext
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20 Posts
Same Problem with 4wd

Hello, my 04 Trailblazer is doing the same thing switching from 2wheel to (auto4wheel) drive without touching the selector switch. Mine seems to do it more while driving at highway speeds and when I let off the accelerator and then accelerate again. You can feel the hubs locking and unlocking along with the transfer case as if I was actually switching the vehicle into auto 4 wheel drive or 4wheel drive. Do I need to replace or update the control module or the selector switch, or both? Also if there is a recall or TSB out there does anyone know the numbers? Thanks
 

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2004 chevy trailblazer_ls
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30 Posts
switch issue

Roadie,

Turning the switch clockwise to counter clockwise used to work for me. I exercise the system every week. Now my 4wd service light stays on and my truck switches gear to 4lo on its own. Could the actuator be going out? To top it off I need to change my front differential seal on the driverside axel. Is that something I can do on my own or should I got to dealer or transmission shop?
 

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2004 gmc
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26,181 Posts
Now my 4wd service light stays on and my truck switches gear to 4lo on its own. Could the actuator be going out?
The Service 4WD light is lit for other reasons. The actuator can make a commanded mode change fail, which will end up with a flashing light on the mode switch. But the actuator and the encoder motor cannot by themselves force a commanded mode change to 4LO. Only the switch, TCCM or the wiring between them can do that.
To top it off I need to change my front differential seal on the driverside axel. Is that something I can do on my own or should I got to dealer or transmission shop?
Many members here have done it. Only you know if you can follow the threads that discuss it and get the right tools to do it properly. It helps if you have a local Harbor Freight. ;)
 

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2002 gmc envoy_slt
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23 Posts
Just to ad my 2 cents worth, my wifes 2002 Envoy was doing very similar things with the 4x4 lights an switching on its own then went blank. I replaced the switch cuz it did that in 2007 and the switch took care of it.
This time the switch would light up at start but then shut down and the 4x4 service light came on. After reading enuff on this wonderful forum I got a used TCCM from a 2004 on Ebay, plugged it in today and ALL IS GOOD!
Thanks to everyone for their input! :woot:
 
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