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Discussion Starter · #1 ·
I've been searching and reading for a while now, but I can't seem to find anyone who has had the same issues as me.

My 4wd does not work. At least, I don't think it does. The light on the dash is on (Service 4wd). The switch lights up like normal when I start the car, then is non responsive. No lights, nothing. It was cheap, so I tried a new switch; same thing. I'm not to sure what mode the truck is stuck in right now. I don't know how to tell. The only way I know how is I tried to do a break stand, would not go, so I believe it's 4Hi. Anyway, I've read about the 4x4 actuator (?) possibly being bad. (from what I know, it's under the car above the skid plate in the front) and maybe the TCCM. Anyone have any ideas?
 

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4HI mode will cause driveline binding if you drive in a circle on pavement. If you have trouble parking, you might be locked in 4HI mode. There's a good chance your TCCM will respond to a power-cycle reset by pulling its fuse (posted in many of the other threads discussing the TCCM). But you didn't fill out your profile so we don't know what year you have. Some 2002 TCCMs had bad hardware that sometimes would refuse to wake up when you turn on the ignition. Those need to be replaced. Therer is also a PCM reflash the dealer needs to install that will do a more reliable job waking up a sleepy TCCM, and that came out in 2003, IIRC.

You should be able to test for the sleep problem by turning on the ignition to get the PCM alive, then pulling the fuse for the TCCM for ten seconds, then putting it back in. If the 4WD system comes alive, that's your problem.

You can tell what mode the transfer case is in if you looked at the encoder motor's control position, but I don't have my shop manual with me at the moment to tell you what position is which.

The front axle actuator is on the right side where the CV shaft plugs in, but if that failed, it wouldn't cause you to be locked into 4HI unless the transfer case encoder motor was also locked up.

What happens if you turn the control switch to 4HI befrore you start the vehicle? If you put it in A4WD, then start the vehicle?

Have you listened to the two noises mwde by the actuator and encoder motor when the system was working correctly, and do you hear either of them now?
 

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Discussion Starter · #3 ·
Sorry, I'm rather new here.

It is a 2002 model. I have pulled both fuses (number 8 under the hood and 48 under the rear seat. Nothing changed. I also disconnected the battery, same deal. Not a change. I don't hear anything at all when using the switch with the car on.

I don't really want to get flamed for this, but is there any way to make the Service 4wd light go away? A fuse I can pull? I was thinking of trading it in anyway, it's just been one headache after another. The transmission lines are all completely rotted, I just had the whole rear axle replaced, the whole underside is rusting. I've never seen a car rust so quickly. It's not even eight years old yet and the floors are rusting! Short of pulling the bulb, is there anyway to get the light off?
 

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Turning off the light is not going to increase its value unless you find an idiot buyer who doesn't test the 4WD system and you're willing to cheat him. I won't flame you, but I won't help you cheat.

Sorry about the rusting issues - you must live in one of those salt-addicted places and not washing it off quickly after it gets covered. After moving out of Massachusetts in 1993, I'm amazed how long mufflers and brake pads have been lasting on my vehicles!
 

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Waking up 2002 Envoy 4WD

Thanks for the tip! My 4WD was inoperable and no lights on the switch were on. I took the above tip and turned my key to "on" and removed fuse #8 for about 10 seconds and plugged it back in. The 4WD lights came on. Fuse #8 on my Envoy is labeled ATC. The service 4WD light came on but went off on the next restart. Hope it lasts. If not, I guess it is a trip to the dealer. Thanks to those that post all of this useful information. I will try to repay the favor with a tip, but doubt I will ever find something that someone hasn't already figured out. Anyway, I will keep trying!
 
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