[hypoxia]

Had the Engine light and Emissions light come on and the torque immediately derated.  This is the Def problem where it does an initial derate and then if you keep driving it will eventually derate to 5 MPH.  I made it to the campground and using Cummins Insite was able to clear the codes but haven't resolved the problem.

Cummins ISX CM2250
Codes 3258 FMI5 SPN4340, Aftertreatment 1 DEF Line Heater 1 Circuit Current below normal or open circuit
3261 FMI 5 SPN 4342 Heater 2 Circuit same detail
3425 FMI 5 SPN 4344 Heater 3 Circuit, same detail
3714 FMI 31 SPN 1569 Engine Protection Torque Derate

edit to reflect current status. The auto reset DEF Line Heater fuse is in the engine compartment fuse box, it checks good but I changed that fuse to a normal fuse.  Line heaters ohms check good.  Could be caused by a bad DEF Controller also.  Travelling today........

Suggestions?

[hypoxia]

Travelled 120 miles today, uneventfully.

[RobSC]

That's good news I think.  Hopefully, you can solve these problems without a shop.

[hypoxia]

I was able to acquire a copy of the rear load center diagrams which show all three UREA DEF Line Heaters power come from F35 20A fuse through K35 CM1-R-12V Relay .  I replaced that relay on the assumption that it may be intermittent.  I have travelled around 700 miles without further problems.

Later model Newell are different with a relay for each line heater and probably variants of that FWIW.

Newell tech support has been outstanding!

[CaptainGizmo]

Great info, Jim!

Glad you may have found the solution/cure.

Just to be super sure, you're saying a RELAY...correct...and not those stupid "resettable fuses" that are so problematic to heat?

I had, and have helped others with, problems from those suckers popping off for a little cooling vacation until I found out how much they don't like HEAT. And, that Load Center...well...not the best place for relays and fuses that don't like heat, huh?

The MERGE RELAY is another culprit of problems aggravated by heat...ask me how I know during my first 100 miles home after purchase! LOL

[hypoxia]

Hi Steve, yes I replaced the little 20A breaker with a fuse and then also replaced the CM1-R-12 relay.  I have been told that those little breakers can cause power problems even if they don't trip.  I took one apart and it is just a contact similar to a relay contact.

You may have seen my post on the Merge relay replacement today.  I think I'll order a spare Merge relay.

[hypoxia]

Just an update, we have travelled around 2500 miles since the derate, no subsequent issues.

[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.

[CaptainGizmo]

SHOOT!!

Keep us posted, and hope you find out what's going on soon.

These things and voltage issues...argh...a real PITA!

Almost any error I get seem to have "LO CRRNT" or some derivative!

[hypoxia]

The only commonality to speak of is when we had the transmission replaced the Doser was disconnected, I think. Always go to the last thing touched. I'm not sure if the heaters are affected by that. All three go through the same fuse and relay (new) to the filter assembly. I'm considering a new wire run as an experiment, it could take a year or so to validate but should be easy. Grrrr