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2002 gmc envoy_sle
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Discussion Starter · #1 ·
Hello all Trailvoy members from Jordan,

and would like to thank you for this wonderfull site, which I have benefited from, like Installing Mirror Turn Signals, which the article by Jman423, made it easy.

I will be cleaning the throtlle body after reading the article by KHill.

My question is, I am having some problems with 4wd with my 02 Envoy, sometimes it engage while I am doing full left or right turn, and lights go on sometimes on 4hi or 4low.

I have been doing some reading about that, and figured fluid changes for the fron and back diff, will do it.

Any suggestion will be helpfull.
2002 Envoy 4wd 85k :thx


on doing the have bough an 2002 Envoy last year, and ma
 

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2004 gmc
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The electrical controls for the 4WD system have very little to do with differential or transfer case fluids.

When you say it engages, do you have the selector switch in 2WD mode, and it changes to 4HI or 4LO without touching the switch?

If that's true, then it's almost certainly just the switch. They have been known to go bad from internal oxidation. You might try one experiment. With the power off, turn the switch through ALL the modes 40-50 times. I always advise people to exercise their system through all the modes regularly, such as every month. This will prevent oxidation buildup and switch failure.

Try that and let us know.

If I was wrong, please explain with more words what you are experiencing when you turn full left or right.
 

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2002 gmc envoy_sle
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Discussion Starter · #3 ·
4X4 Problems

Thanks Roadie for your quick reponse.

The problem is as follows, when I am driving at 2wd, come to complete stop, and want to make full left or right turn, the four wheel drive engages, and light switch will be on 4hi and sometimes is on 2hi, and I have to switch back to 2wd.

This problem always happen when I want to make a u turn, and it engages the 4wd.

I am going to try what you have said, and will let you know.

Again thank you for your response and attention.

Free Landjo
 

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2002 gmc envoy_sle
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Discussion Starter · #4 ·
4X4 Problem help

Hello eveybody and specially Roadie,

I have posted earlier my problem with 4X4 and I did what you said about moving the selctor between modes between 40-50 times, and the problem did not go.

In exact detalis how it used to happen

When I am driving at 2hi, come to complete stop, and want to make full left or right turn, the four wheel drive engages, and light switch will be on 4hi and sometimes it is on 4lo, and I have to switch back to 2wd.

This problem also happen when I want to make a u turn, and it engages the 4wd.

I took it to the dealer to check it out and to change the differential fluids, which they did and also checked the 4 wheel.
Their diagnosis where that everything is fine and no problems were found.

two days after being at the dealer, the 4 wheel drive engaged while I am driving staight and at speed of 45 KM and had to shift into neutral and slow down and turn the slector switch to 2 hi.

I need help please, is there a way to diconnect the 4 wheel drive until I found a way to figure out the problem, and not having it engages anymore.

Ghaith :thx
 

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2004 gmc
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Disconnecting is easy - remove fuse #8 under the hood, and fuse #48 from the rear fuse block.

As to your problem, if the dealer found nothing wrong, did they at least reflash your TCCM? 2002 models had intermittent TCCM problems, and some of the modules were bad. And all of them needed new software loaded. Most of those problems related to a failure to wake up when the vehicle was started, so the TCCM would ignore the selector switch.

But they should have updated the software automatically as part of their troubleshooting process. Did they?

Anyway, your problem still looks like a failure of the switch to communicate to the TCCM or the TCCM is bad. At least you seem to have no problem with the actuator or the encoder motor or the transfer case.

It's possible to troubleshoot switch->TCCM communication problems by using a digital voltmeter to look at the signals, but for intermittent problems like yours, that's very difficult. If you have a wiring harness problem in the vicinity of the steering wheel, the dealer should have found that if they inspected for it. I recommend asking them if they looked at the wiring for chafing. Since the switch and the TCCM are on opposite sides of the steering wheel, I can imagine a bit of wire insulation could be abraded and causing an intermittent short to ground.

But other than that, the most common way is to start swapping parts. If you have a friend with a trailblazer, swap the TCCM or the switch and see if the problem moves. Otherwise it will cost money with no guarantee of a fix, to purchase replacement parts and put them in. Sorry. I don't have any better advice.
 

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Discussion Starter · #6 ·
Thanks

Dear Roadie,

Thanks a lot for the help,

I will go back to the dealer and discuss with them what they did and I will be using your suggestions.

Unfortunately all my friends who have either an Envoy or Trailblazer they bought 2 wheel drive to stay away fromt the problems of the 4 wheel drive, and I will just diconnect the 4 wheel drive if the problem is not solved.

This might sound strange but how the TCCM look like.

Thanks again for all your help, and I like your car alot and what you did and have watched all the videos on the Youtube

Best Regards,

Free Landjo
Ghaith :thx
 

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2004 gmc
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The TCCM is item #2. Mounted to the dashboard panel above the driver's left knee. You can see it pretty easily if you remove the dashboard access panel on the far left side - the one that's hidden when the door is closed.

 
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