Cat C7 starts, idles, but won't rev up in gear.

I'm not overly trusting in those filter minders. We had them on all our fire trucks and, just like when I changed it on our motor home, they all read the same thing when we changed them on the fire trucks after quite a few miles. Mine on our coach, was never changed prior to 50K miles and, it read about half way. I changed the air filter, and reset it and, it read about half way. So, it's simply a "catastrophic" reading that I will have to pay attention to.
Scott