I always keep it at 100% full.
It cleared the code once then 35 miles later, no engine light but said it was going to to 5mph after the next 150 miles.
I was 450+ miles away from home yesterday.
Keeping it full is your problem. I bought a new aerial fire truck at work (over $1M), and it was the first the department had with DEF. They "topped it off" 2-3 times a WEEK, so the level sensor never moved. Threw a code for a defective sensor and the entire tank had to be replaced under warranty. 6 weeks later, same thing. That's when we found the root cause. It's one of the many safeties required by the government to make sure you don't mess with the system. let it go down to AT LEAST 1/2 is what Cummins told us...
The last time I filled it right up to the top was when it was just above 1/4 tank.
I was towing when it went down.
Now 800 miles later driving with no trailer, the gauge hadn't moved.
I've been driving it every day since to get that gauge to come down some.
