Another quirk I should add. We had a new Morooka dumper with a Cat engine on rent at a job in WV for several months. During that period I had to call a local Cat mechanic to deal with DEF issue. Long story short, after talking to a number of people involved to come to a conclusion I determined that the job site "rules" required all operators to turn equipment battery disconnect switches to the OFF position when they shut down their respective machine. Well, this interrupted the DEF purge cycle mentioned by Paul Council, sent that Cat system into flip out mode on next start up. Machines that have ECU/keyswitch controlled battery disconnects don't have this problem, but on this job site, if the machine has a manual switch battery disconnect it was a problem. Again, have to educate the end user.