Turn the truck key to the on position. fully depress the accelerator
pedal 3 times in 5 seconds. turn the ignition off. Restart. It may take
several tries to get it done.
If you have a trailblazer with all the buttons on the steering wheel.
You DO NOT reset the oil % with the three pedal push method. Instead
you turn the switch to cranking position(two clicks) when you see the
drivers display, depress button until you get to the oil% screen. Then
depress and hold the "return" button it's the one that looks exactly
like the symbol on the (enter) key of your computer. Voila! it resets
back to 100% oil life!