2003 H2
So, a little history...
About two winters ago I took the daughter up to the mountains to check out a massive snow storm. We found the most awesome virgin snow trails you can imagine. We had a lot of fun. On our way home there is a small, maybe 8 foot high, decently steep section that I had to climb. Standard AWD didn't cut it and I didn't want to get too much momentum so I switched to 4Hi and spun my way up.I switched back to standard AWD and then i noticed all the 4WD lights were out, right after I heard her disengage. No combination of button presses, engine on or off would do anything. Ran just fine.A few weeks later, a rather warm morning, I go out to warm her up and lights are back on like nothing happened.

Skip ahead to this last summer. No issues until this day. A really gnarly, steep, rocky climb had me in 4L with locker engaged. She practically idled up. I go to put her back in her natural state and I can hear the usual "clunk" and then another clunk...and still in 4L. Hmmm. I try a couple more times but nothing. I turn it off, disco battery for 20 minutes and again, nothing. I try every combo (not many) I can, from 4Lo to 4Hi lock, to 4...nooothing. I don't want to constantly be engaging/disengaging so I stop and take a break to think. I'm literally about 45 miles from the nearest paved road, 20 miles from a cell signal. There is no way I am going to drive that far in 4lo. I get the idea to have the negative battery cable undone, but still connected. I tie some cordage to the cable and run it to the drivers seat. The idea is to to hit the 4H button and right when I hear it gearing, I yank the negative and hope this stupid idea works. I tried it first by just hitting the button then turning the car off but it's still getting power and finishes. So I try my method and F me...it worked!

Skip ahead to the other day...
I was pulling out a couple in their Odyssey Mini van that were out sight seeing in the snow and slid into a ditch.I get them out and noticed the same issue. No lights, pressing the buttons doesn't do anything this time. Not quite sure where to look first? Thankfully the AWD is a strong as it is and was able to pull them out without needing to lock it down or anything. Anyway, any thoughts? Anything I can check?

 

there is a good writeup here but our module would be located on the steering column i think it has a borg warner lable on it https://carfromjapan.com/article/car...dule-symptoms/

 

My first guess would be the 4WD actuator that mounts to the transfer case. GM parts number 89059688. Really easy to replace, solved all my issues that you are describing.

 

I'll give my two cents. Do you switch 4wd modes often? I know when it sits for a long time, the actuator becomes seized slightly and throws a 4x4 error which turns the lights off when you switch. What fixed it for me was changing from 4hi to 4hiLock 20-40 times, then switching it back to 4hilock and then do it from 4hiLock to 4Lo 10-20 times. This usually clears up whatever crap is gummed up in there so the motor turns freely and the sensor can get a reading.

If this doesn't work, I would replace the sensor on the T-case or the actuator itself.

 

I will add to only buy OEM parts, the Dorman stuff is junk and AC Delco from Amazon or mostly counterfeit. I buy my GM stuff from my local Chevy dealer to make sure I don't get fakes.