2002 GMC Envoy 4 WD??

[DeeGee]

Just replaced the battery on my 4WD Envoy.  The "Service 4 WD" light came on after battery replaced.  Too bad I can't find the manual to see what gives.   Any comments, cautions, etc.    DG

[quickdtoo]

That's a know issue with em, I used to have an '02 Trailblazer with the same problem, the 4WD switch is the culprit most likely, there's a TSB on it. You can do a search at the Envoy forum on Edmunds. Take it to an Autozone and have em hook up a code reader and see it there are any DTCs set, it's free.

Tim

http://townhall-talk.edmunds.com/WebX/.ef00533/

[Lloyd Smale]

try diconecting the battery again waiting 5 minutes and hooking it back up. It might clear the code.

[quickdtoo]

If there is a code set, disconnecting the battery again may put the light out, but the code that may help diagnose the problem that caused the light in the first place will may be lost. I would cycle the 4WD switch through all modes while in neutral to see if that helps. If the light on the switch acts normally, then it's probably not the switch. If all the mode lights on the swiitch blink, I think a new switch is in your future.

Tim

[DeeGee]

Appreciate the comments.   AutoZone can't read the codes on drive trains, only engine.

When I first fired the engine, after changing the battery, all four lights on the 4WD dash switch come on all at once.  That's when the "service 4WD" light came on, no lights lite on the dash switch and the service light stays on.  Did the battery disconnect trick, neutral and switching between 4WD modes.  No lights will come on at any of the four settings.   Put the switch in 4HI. found a large patch of ice so that all wheels on on the slick,  gunned the engine and only back wheels spun.   What say?    Defective switch??
Thanks     DG

[quickdtoo]

With the switch being a known issue, I'd take it to the dealer and see if they'll replace it, even tho it's out of warranty unless you have and extended warranty, they might still replace it in good faith, worth a try. Otherwise, yes, I'd do the swtich, although it still could be something else.

Tim