Demo/legacy repair — real data lives at cases posted by signed-in technicians.
Cummins ISX15 derate after regen — SPN 3251 FMI 0 recurring
Peterbilt 579 · Cummins ISX15
AI Summary
Verified fix across 22 cases: cracked DPF substrate from hydro-lock during previous coolant leak repair. Replace DPF, verify EGR cooler, reset ash accumulator.
Symptoms
Engine derates to 55% power within 30 min of forced regen. DPF pressure high at idle.
Verified Repair
Replaced DPF assembly, EGR cooler, reset ash counters. Regen cycle stable at 100% load.