Originally Posted by mbaessler
Akinny: I had it done at the dealership. Ground in shop is pretty flat. Also don't know if it's close to full does it register full than drop off quickly?
On retail delivery, my selling dealer didn't fill the DEF tank like they were supposed to, so my local dealer agreed to fill it from their brand new 50 gallon drum for good will. I watched the local dealer fill it with the ignition on (engine not started) so we could watch the DEF gauge. The DEF gauge moved up every so often during the fill, but not smoothly. It had significant lag around 30 seconds or so. It registered full just as it spilled out the filler neck, so it would have likely registered full before that if the fill were slower.
Maybe yours just had an anomalous reading during fill that fixed itself after the next sensor update? From what I saw it updates maybe every 30 seconds, so I would expect it to stabilize within a couple minutes from the fill.
I think it makes sense to note your mileage and DEF % and check again in 500 miles to get a sense of your actual DEF consumption.
It's probably fine and there was just a sensor hiccup. From what I understand, it's actually an ultrasonic sensor (like sonar), so it's more of an estimate from multiple readings. With the fluid swishing around during a fill, I could see the sensor getting some erroneous readings until things settled down.