well i cant see what pics were posted due to a firewall at work.. but
ive got a 90 k5 blazer, i know its not a hummer but its still gm and id be willing to bet have the same issues. anyway u might want to get it looked at. mine was doing that then it started blinking. 2 days later i lost my brakes. im being told it has to do with one of a few things
1. your fluid level is low. but u said its not
2. your anti lock system is having issues. the light will come on if the system is sensing a difference in pressure between the front and rear brakes. i was told to look for leaks in the calipers and wheel cyl.s mine was good there.
3. the last was the anitlock system was taking a crap.
might be some things to look into. i know its not from an h2 but i spent hours looking for this info. u would think it would be in the manual or a repair man. but i couldnt find any info on it
good luck