I started up my H2 today...mind you, it basically sits in the garage and I take it out about every two weeks or so. It has 24K miles 07' Lux model. Started her up....was fine. Let it warm up, and then realized I had to go back into my house. Shut it off, and turned back on....went to go up the road and the Service 4WD message came up on the dash. I turned off the message.
The 2 drove fine...no issues. I called Onstar and they said the 2 was giving a code of 4wd transfer case problem. I stopped and was on dirt and went into 4wd hi lock, with no issues whatsoever.....and then back to regular 4 hi. It ran fine the rest of the day....no issues.
I'm just curious if this is a common issue from sitting too much or if there is something that needs to go in for service immediately??? Any advice would be great!

 

Mine did that and all I did was unplug the fuse for a couple of minutes and put back in. No problems for over 2 months now. Well battery did go out but that was it.

 

No clue if it uses the same or similar electronics as other GM vehicles, but a very similar thing happened with my wife's Avalanche. For those and similar trucks it's a common problem - it's the electronics that goes bad, the TC itself is fine.

 

Same thing happened in wifes Tahoe. Ended up being a bad sensor.

 

I would bet that the transfer case motor is having some difficulty making the switch or the sensor is sending bad signals. Worst likely case is the transfer case motor, about $600.00 done at a GM dealer. Just had to replace mine but the dealer decided not to charge me because the Hummer was only a couple days out of warranty and they care about the service they provide.

 

My 2003 H-2 did the same thing and I took it to the "Stealership". They told me that the transfer case motor was going bad and that I needed a new one. They also told me that after the new one was put in that it would have to be programmed. They wanted $700 to fix it and make it stop saying (service 4WD). This message would come up almost every day but being a poor guy, I had to do what I do best....NOTHING. I ignored the problem until one day my son played the stereo all night until the battery went dead and the truck had to be jump started. Ever since that day, I haven't gotten the service 4wd prompt. It's been about 8 months now and the problem just went away. I suppose you could just unhook your battery for a while (both cables) and let all the codes clear. You may get lucky and that clear it up. No, I haven't thanked my son for running it dead.

 

I had this problem on my '06 for about 6 months. It took Onstar diagnostic codes to finally get the dealer to fix it. They did a software upgrade and replaced the 4wd switch and have seen no more issues.

I had previously read that the contacts on the transfer case shift module can get coroded contatcs from lack of use. After shifting mine back and forth from 4wd hight to 4wd low 50+ times over 3 months, I gave up on that as the problem.

 

Sounds like you owe your son a nice dinner out or something.

 

I had this problem last year when the first big snow hit here in Utah. I went to engage the 4WD and got the service 4wd error message. Didn't hear anything happening down below (shifting). Two weeks later just before I took it to my local shop I decided to give it one more try and it worked perfectly like it had never had any issue. (it had been displaying the same error code for the two weeks)
Now, here we are in winter again and I'd like to be able to use my 4WD. Just had our first big snow and what do you know....no workie. Same problem as last year. I just talked to a mechanic friend of mine that has worked on plenty of GM vehicles. He said it's one of 3 things:
1. The encoder motor - big $$ - must be replaced. All that jazz.
2. The ground wire or control wire for encoder motor. He mentioned that sometimes these get corroded and cause issue. East fix if I can locate.
3. Electrical control in the fuse area. He said that some models get some water down in there (fuse section at driver front) and it causes issues. I have a small water leak in the driver door which drips into this area so could be.

ANYONE know for sure? I'm having a hard time figuring this one out due to it being somewhat intermittent. I need my 4WD to be working STAT so I can take this beast up into the mountains for some snowboarding!
Any help is greatly appreciated! Thanks!

 

Mine 2004 H2 displays it every time I drive for more than 2 years. I had a shop to check if the lock is engaged or not when the display shows. And it is engaged but displaying service 4wd. Since then whenever it displays, I just reset it and forget about it.

BTW, H2 is permanent 4wd. You are always getting 4wd traction. When you need extra then you lock it up.