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2015 CM2350

Got the following codes today and truck derated from 25%, 75% to stop:

- SPN 4340 - FMI 5 - Def exhauster fluid line heater 1 state - current below normal
- SPN 6802 - FMI 31 - DEF System frozen

DEF is not frozen. Def is 80%. Checked all the connectors at the DEF pump for physical damage and connection, nothing to note. I changed out all of the relays (3) and the 15 amp fuse on the aftertreatment box, no avail.

When running data logger, i can see that the 4 heaters are on. But Def temp stays between 55 and 60 F. Temp right now here is about 40 F.

Any tips or tricks besides the quickserve troubleshooting.

Just wanted to give a shout out to Running Rough. I had the Covid this week, and he was very understanding and patient working with me to get my cm2350 breathing again.

Just for info for anyone else, it was the DEF heater line, had put the truck to a crawl in about 6 hours following quickserve procedures.