My son is looking at a 2004 Avalanche. 94,600 miles and every option available for the year. It's owned by a banker and he ordered it with everything. He can get it for about $10,500.Anyway, I test drove it and the "service 4 wheel drive" light popped on. Does this indicate a serious condition, or is it a "take it to the dealer and reset it" sort of thing? Any of you folks know anything about that code? Thanks!

I've seen that light on mine a few times. I never had it looked at. Still going fine. I wonder if that is one of those lights that is set to come on after a set amount of miles like the "change oil" message.

I have an '04 Av. It had that problem for about 6 months as it got more and more strange. The buttons eventually won't work, and you will be stuck in 2 wheel drive.
It was fixed by changing the device on the transfer case that engages the all-wheel drive. Sorry I can't remember the part name. I'll see if I can find the repair ticket.

Thanks for the responses. ReEntryRacer, was the repair very expensive?

Had a Bronco that had electronic transfer case engagement solenoid issues like that.
Was told by the dealer and a 4x4 site I used to frequent that lack of use gummed the movement.

It was a couple of years ago, and I can't remember, but I think I would if it was outrageous!

Serivce 4 wheel drive light indicates a problem with the 4 wheel drive system, like the check engine light for the engine. It is not a maintence service light. It has found a problem and like the check engine light it may be something small and not affect the system much. I would get it checked out just to be sure. The selector motors can be a little pricey but are very simple to replace.

I just left my local Chevy dealer. I spoke with a buddy that has worked there forever, and he told me about the same thing. He's a parts man and said most of the time it's the encoder motor, or a ??? module. The encoder would set me back $413.00, and the module is $310.00. He did say to have it scanned, looked at, or what ever before buying either of those parts. Thanks for the input.

Both seem to be common problems with 4X4's around here. The funny thing is most of the time customers say "I never use 4 wheel drive". I wonder if that is part of the problem. I suggest to customers to cycle/drive every now and again through all functions. At low speeds of course.

On my 2000 Silverado Z71 with AutoTrac NP246 transfer case. I got the Service 4WD light. It was caused by a bad 4wd selector switch on the dash. It's very common for the Silverado's and may also pertain to your Avalanche.

If it's Autotrac be sure to change the fluid out as well with the blue stuff.

Again, thanks for all the information. He hasn't bought the truck yet, and the banker that bought it new, "almost never used 4 wheel drive, and NEVER took it off-road." I've heard of issues like this when a system isn't used often enough. Maybe this is one of those. Again, I can't thank you enough.

Rocky, do you work at a Chevy dealer?

Yup, the info here is correct - it's either the encoder or the 4wd module. LACK of use is what kills 'em.

Yes see quite a few encoder motors on these. The older ones the switch assembly was an issue.
There is some updated TCCM module software too.
Getting the codes out of it is a good starting point.

Can anyone other than a GM dealer scan these things?

I worked at one for a while but left due to money. I am the Lead Tech for Coca Cola Fleet Dept. in York county. I am always working on cars on the side if you need help. The only bad thing is I live a little more than an hour away from Chester. I do have the capability to scan and troubleshoot it.

Nice. You sound like my hubby, ex-GM mechanic!

Yep I am. I make more money fixing them on the side. I charge extra for Fords

LOL! One time I had to rent a car and just for kicks I rented a Mudstain V6 convertible. Went to pick up hubby at his work in this thing just to see the look on his face, it was PRICELESS!!!!

Damn that does sound like me.