2002 Envoy goes to 4WD low

[rdwr01]

Sometimes my daughter's 2002 Envoy will be in wheel low when she starts it. Sometimes she can get it out but recently she couldn't. seems to be getting worse. She has tried moving it slowly then changing on the move at 2mph or stopping and changing. Nothing seems to be the best.
Last time a GM dealers said he could fix for 600 bucks.
Any ideas on what is wrong? Is it something I might fix for her?

[maxwedge]

The dash switch was the most common issue with this, BTW the only way to normally engage and disengage 4w lo is in neutral at a dead stand still. If the dash monitor lite on the switch randomly changes to 4wl lo without touching the switch itself, then it is bad, if it is in 4w lo and the lite says 2wd, the transfer case control module is bad, which also can be an issue.

[rdwr01]

thanks,
2wd lite is on and 4wd low lite flashing. If it is dash switch, is that hard to replace? Would you try it b4 transfer case module?
If it is the transfer control case module, is that hard or expensive to replace?

[maxwedge]

Switch you can do yourself. The module must be reprogrammed when installed. They are expensive, check GMpartsdirect.com

[rdwr01]

It was the dash switch, thanks

[maxwedge]

Great, thanks for posting back!