2018 Freightliner Cascadia DD15 - Forced Regen Fails and Stuck in 5 MPH Derate

Question

My truck is stuck in a 5 MPH derate and I can't get a parked regen to complete. It starts the process and ramps up RPMs, but then aborts after about 10 minutes with a 'Low Ash Cleanliness' message and various SCR efficiency codes.

dieselmike88 · Accepted Answer

Found the issue was a completely crystalized DEF decomposition pipe and a failing DEF Dosier Valve (Part# A0001405139). The build-up was so thick it restricted flow, causing the SCR codes and forcing the derate. After chipping out the urea crystals and replacing the valve, I had to use DiagnosticLink to perform an 'ACM Aftertreatment Device Reset' and a 'SCR ADS Self-Check' to clear the 5 MPH lock before a final 45-minute parked regen finished successfully.

Ashley Park · Answer

Run a DEF quantity test using DiagnosticLink. Even if the nozzle is clean, the pump might not be building enough pressure to atomize the fluid properly through the mixer.

Greg Walters · Answer

Have you looked at the 7th injector (hydrocarbon doser)? If that fuel injector is clogged, you won't get enough heat into the DPF to sustain the regen, causing an abort.

Sam Holloway · Answer

Check your outlet NOx sensor readings. If the sensor is skewed, the ACM won't allow the regen to finish because it doesn't see the conversion efficiency it expects.

2018 Freightliner Cascadia DD15 - Forced Regen Fails and Stuck in 5 MPH Derate

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