4x4 problem on 2003 sanoma crew cab

Drove around in the snow today for about 10 miles. I put it in 4HI, drove about 2-4 miles at low speed, around 35mph. I have never ruff housed this truck and never engage the 4hi while moving forward. NOW the darn thing will NOT go into 4HI. It WILL go into 4LO. I know nothing about the mechanics of a vehicle and feel lost. Any info would be very much appreciated. The truck has 45000 highway miles, and has only been in 4 wheel drive just a handfull of times(snow) Thank you, Stevie

There is a relay mounted on the drivers side near the top of the transmission that could be bad but I think you may have the same problem I did on my 2002....there is a vacuum line that connects there also. It seems that when the service tech was checking the transfer case fluid level, he somehow disconnected the vacuum line. Plugged it back in....works great. The relay problem showed up on my 1988 S10 Blazer. Replaced it ( cost around 45 bucks for the part...just unplug the harness, unscrew old relay, screw in new, plug harness back in.) Never had any more problems with it.

Onother option: Those are notorious for "freezing up" sometimes if you warm them up they will work again.
If that is not it, it is usually the encoder motor on the transfer case. They are fairly easy to change. They cost about $150. If it's not that it's the transfer case control module (TCCM) $300.
goodluck

Remove the negative battery cable from the battery for 30 minutes and then reattach.

The 4x4 should work now.