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2002 chevy trailblazer_lt
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13 Posts
Discussion Starter · #1 ·
So, here's the rundown of what's been going on , what i've done and where i'm at. The Service 4WD light has been on steady while in 2WD in all kinds of weather, rain, snow or shine, for about a year now, but occasionally goes away and 4WD does work, but then light comes back on and away goes 4WD. The 2WD selector switch light is on steady as it should be, but I changed it with a new switch as it was only 20$ or so, but the problem remained. Then i bought and installed a new encoder motor, but the problem remains. Didn't want to keep throwing cash into parts that i apparently don't need , so i bit the bullet and had the truck scanned with the Tec 2 scan tool for $100. They came up with front differential actuator is not engaging, and recommended replacing it. So i purchased a new actuator and swapped it out , but guess what? The problem remains. :mad: The intemittancy is what bothers me. I am an Electrician and know intermittent issues are typically an electrical connection issue, but i'm not sure how to even start to troubleshoot this. I think my next step is checking the connectors on the TCCM to see how those look. The mechanics said the Tec 2 didn't see any faults other than the actuator not engaging, no TCCM codes or anything else. But, of course, they weren't able to give me a print out of what the tool found. :mad: The only bright spot in all this , i guess, is that i did all this swapping out myself and saved 600$ or so in labor alone! And i have this amazing website trailvoy to thank for that! Thanks to all who contribute here, your knowledge is invaluable. :) Now, what's my next step?:bonk:
 

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2002 gmc envoy_sle
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5 Posts
same issue with 02 envoy

I'v been having the same exact issues with my 4x4. if im driving on icy roads in awd the switch will start flashing and trying to change to 4 low and then the light will go on the dash. If i restart the suv it will go away sometimes for a while then sometimes it comes on after 50 miles. let me know if you find a solution and me the same.
 

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2003 chevy trailblazer_ls
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12 Posts
4x4 intermittently working

So with my t/b, if the selctor switch is at AWD, the AWD system functions correctly and engages the front axel when slippage occurs. With the selector in the 4W HI or LO positions the front axel does not engage at all, but the transmission is in the correct gear (Hi/Lo). To me this seems like it could be a transfer control module. Anyone have same issue with positive results?

Oh, I should also mention that the service 4WD light intermittently comes on and the little red slash appears on the 4wd selector switch, and nothing works with the 4WD

Thanks,
Idahosnoman
 

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2002 gmc envoy_slt
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1 Posts
Flashing Mode Lights - Changes from 2Hi to other modes

2002 Envoy SLT, 122K

- The 4x4 mode lights flash upon start up (some days) and other days not

- When the problem starts, flashing mode lights - jumps from 2Hi to another mode while in Drive and on some occasions when making sharp turns - it makes a loud humming noise (moves forward very slowly); I stop, change the mode back to 2Hi, let it sit for a moment and drives fine

- Dealership can't diagnose until it's actually doing it or until the Service 4x4 light is on which hasn't came on. Another mechanic has been unable to find the source of the problem even after letting him keep it for a month; claims the diagnosis would be based on trial & error from a possible electrical, module, and/or computer problem; said he doubts that it's the transfer case. His suggestion: "Get rid of it." :no:

- It's been randomly happening over the past year; it happened last in August '11 and would barely move forward in Drive; wouldn't go in Reverse; it sat for about an hour while waiting for a tow truck; tow service was not needed as it drove fine afterward - had it checked; they couldn't find a thing; no flashing mode lights on start up nor in drive; drove fine until last week. :undecided

Any suggestions would be greatly appreciated.:thx
 

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2002 gmc envoy_sle
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9 Posts
Oh no!

I had all the same problems and changed all the same parts with exact results. Sorry to say my problem turned out to be the front differential. There were some stripped parts that would not allow the four wheel drive to engage. Hope it's not the problem for you guys but like I said, I went through all the same changes and that's where I ended up. Good luck!:bonk:
 

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2002 gmc envoy_sle
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5 Posts
i checked my voy over today and when i try to switch from 2 wd to whatever else i get some noise from the middle of the voy. the noise is the actuater trying to switch into or out of 4x4 i think. The area it is making noise must be the transfer case so should i pop the round oil filter looking thing off and check it out
 

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2002 gmc envoy_sle
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9 Posts
Oh no update

Got the front diff finished today and problem solved. Too bad for me but I have an entire new four wheel drive system by the time I trackEd down the real Problem:hail:
 

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2004 chevy trailblazer_ls
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4 Posts
Yesterday Snow

No problems at all yesterday in the snow. Warning light came on after a few miles in 4Hi in the snow, but 4Hi worked beautifully. Don't really need to drive much in the snow, so i think I'll hold off any more dealer visits if it can keep resetting itself.
 
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