Originally Posted by wireman
The DEF gauge still shows 100% full. I would think the level should have gone down after the amount of mileage I've driven.
Are you certain you're reading the gauge correctly? The UI geniuses at FCA thought it would be clever & exciting to replace the expected "F" on the DEF gauge with "100%".
That is to say the 100% on that screen never changes, even if the tank is empty. It merely indicates the "Full" end of the gauge. It's the indicator bar that moves right to left as DEF is consumed.
Also, the DEF level is based on a crappy ultrasonic sensor in the tank, which is so imprecise that they "smooth" its readings to avoid having it fluctuate wildly. This is why you must always add at least 1 gallon of DEF at a time. If you don't add at least that much the algorithm will presume the ultrasonic gauge is smoking crack again and will suppress the updated fill level readings.