[hypoxia]

It's Back!  After 3900 uneventful miles and 94 engine hours, all 3 DEF heater lines showed "Current below normal or open circuit"  The Check Engine Light illuminated as soon as I turned the key switch to on, hadn't moved it to start.  The only thing I did differently was use the AquaHot to warm the engine.  Of course it was a day of mountain driving and I elected to drive & see how much pep it had.  Ha, the 25% Torque Derate kicked in after an hour as I started up the longest crawl, 19 MPH at the bottom and slowing.  I pulled over, got the computer out and cleared the codes, back to normal on that hill 37 MPH.

Time to trace some wiring.  I have 3 weeks until the next hill climb.