Electrical grimlins. Need advice.

06 silverado excab 4x4 5.3 no mods 110k. Driving down the road when service 4x4 comes on, then moments latter service air bags. Truck feels like it went into limp mode. Fuel mileage goes to crap and starts shifting hard. I'm at whits end trying to find out what's up code scanner only says P2771 and that's it. Any help would be much appreciated.

The 4wd control switches are notorious for having internal failures like interm shorts causing those symptoms. We used to change a lot of them when I worked for Chevy

I was able to just hit all the solder joints in mine with my soldering iron to fix mine. Seems a lot of them had bad solder joints.