Aftertreatment DPF Regeneration Requested for Long Period - Derate
What does CUMMINS-3727 mean?
The CUMMINS-3727 (Cummins) diesel fault code means: Aftertreatment DPF Regeneration Requested for Long Period - Derate. This is a moderate severity code.
Common Symptoms
- DPF lamp illuminated on dash
- Active regeneration messages on dash
- Increased backpressure and reduced power
- Higher than normal fuel consumption
- Black smoke out of stack when accelerating
Probable Causes (Ranked by Likelihood)
- DPF severely loaded with soot requiring forced regen Very Likely
- Excessive ash accumulation (cleaning required) Likely
- Failed differential pressure sensor or hoses plugged Likely
- Short-trip duty cycle prevented passive regen Possible
- Faulty DOC (upstream oxidation catalyst) Possible
- Aftertreatment fuel injector stuck or clogged Less Likely
Step-by-Step Diagnostic Procedure
Connect INSITE and read soot load estimate, differential pressure, and last regen status for fault 3727.
Park truck safely in non-combustible area with parking brake and initiate a parked/forced regeneration via INSITE.
If forced regen fails or DPF is above 100% soot load, remove DPF for professional cleaning (ash + soot bake).
Inspect differential pressure sensor hoses at DPF for soot clogging or kinks -- replace if obstructed.
Verify DOC inlet temperature rises above 570 degrees F during regen command (DOC functional check).
Inspect aftertreatment fuel doser or dosing injector for clogging; clean or replace as needed.
Frequently Asked Questions
What is Cummins fault code 3727?
Cummins fault code 3727 indicates: Aftertreatment DPF Regeneration Requested for Long Period - Derate. It is a moderate-severity fault in the aftertreatment or emissions system.
Can I drive with Cummins fault code 3727?
Short-term, yes, but the engine will enter derate (typically starting at 55 mph and progressing to 5 mph for emissions faults). Drive directly to a repair facility. Do not defer this fault more than a few operating hours.
How much does it cost to fix Cummins fault 3727?
Repair cost is approximately $200-$1,500 including parts, labor, and any dealer programming required. DIY repairs (sensor replacement) fall at the low end; pump, aftertreatment, or ECM work falls at the high end and usually requires INSITE diagnostic software.