Ultraguage Issue

During my 25K service a few weeks ago, the dealership replaced my battery. When I got in the truck to leave, I noticed that my ABS and VSC lights were both on solid (you'd think they'd have noticed it too, but that's another issue). They called out a svc manager who took it back in and reset everything. He said he ran a complete diagnostic and everything was good to go.

Fast-forward to a couple days ago and I had to disconnect the positive battery cable in order to remove an accesory wire I no longer needed. When I got in the truck the next morning, lo and behold my ABS and VSC lights were on solid again and my BRAKE light was flashing some sort of code pattern.

My Ultraguage was blank so I unplugged/replugged it with the truck running and it reset itself. That didn't change the dash lights though, but when I shut the truck off then restarted it, everything went back to normal.

So, apparently having the UG plugged in, but not functioning was what was causing the idiot lights all along and the svc mgr never needed to do the whole diagnostic scan. Moral of the story: If you have an Ultraguage, unplug it before disconnecting your battery, then plug it back in once everything's up and running again. I guess.

 

Dang. It seems like there are infinite possibilities to trigger these lights. I guess.

 

Scan gauge has a cap in it for memory. I suspect the scan gauge trying to feed a small about of power backwards in the truck as the cap discharges. In turn feeding power to other low volatge system causing the errors.