4-wheel drive


Old 12-16-03, 08:55 PM
Thread Starter
Join Date: Nov 2002
Location: Canada
Posts: 105
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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Old 12-17-03, 02:09 AM
Join Date: Dec 2002
Location: Connetisuck
Posts: 162
Sounds like a problem with the actuator. My suggestion is to buy the OEM Manual if you plan on diagnosing it yourself.
Old 12-17-03, 03:49 AM
Desi501's Avatar
Join Date: Oct 2003
Location: Boynton Beach Florida
Posts: 2,207
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.
Old 12-17-03, 06:03 AM
carguyinva's Avatar
Join Date: Nov 2003
Location: Shenandoah Valley
Posts: 1,147

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!
Old 12-17-03, 04:58 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
Posts: 2,417
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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