Distance with DEF code?

[barf]

I've seen the water in DEF light come on before, only when I was really low on DEF, and then filling up the DEF fixed it. This time, unfortunately, whole different problem. I had over 1/2 tank DEF and when I fueled, I didn't even take on any DEF.

I have some really good reasons to believe the problem is the DEF pump, which is getting replaced here in the morning. No, I didn't make my delivery yet. For approx $1500 for the pump, I sure hope I'm correct.

I don't have Calterm working yet either, but if I knew for sure that it would've gotten me home, I would have paid to download it. I'm really hoping to get to Georgia to get my truck looked at. Maybe, maybe not, get some drastic program changes done.

I'm curious to know though, what happens when a truck runs many miles without using any DEF? Other than the ECM wanting to derate, is there any harm that could occur?