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4-wheel drive

spells's Avatar

Join Date: Nov 2002
Posts: 105

12-16-03, 08:55 PM   #1  
4-wheel drive

I've got a 1999 GMC Envoy 4.3L with the electronic 4wd selection, however when I put it in auto mode or any of the others for that matter the indicator just flashes for a while the returns to 2w HI. I never feel the wheels engage also checked it on a hoist to see if the do..nada. Any ideas?

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YamahaWolverine's Avatar

Join Date: Dec 2002
Posts: 162

12-17-03, 02:09 AM   #2  
Sounds like a problem with the actuator. My suggestion is to buy the OEM Manual if you plan on diagnosing it yourself.

Desi501's Avatar

Join Date: Oct 2003
Posts: 2,207

12-17-03, 03:49 AM   #3  
The flashing light is the module's way of telling you it has seen an electronic problem and is disabling the system. That diagnosis is a little beyond a DIY and probavly should go to the dealer or a high tech independent.

carguyinva's Avatar

Join Date: Nov 2003
Posts: 1,147

12-17-03, 06:03 AM   #4  

if you want to "swag" it...they had alot of trouble with the switches (i have a 2000 Tahoe and mine failed...same with my best friends 2000 Sierra). desi is right, the flashing light is telling you something and someone with a scan tool should be able to get the code for you (don't know if autozone can do this for you...i think they can only get engine codes)...if it has set a switch code, replace the switch...good luck!

davo's Avatar

Join Date: Apr 2002
Posts: 2,417

12-17-03, 04:58 PM   #5  
B2725 is Auto transfer case mode switch malfunction(the switch on the dash).Most likely cause followed by the encoder motor(electric motor on the transfer case).If you don't wan't to pay for diagnostics throw a mode switch in it It is the cheapest shot after checking the atc fuse.Which I hope you have done already.I think you need a tech2 to read transfer case codes(GM tool).

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