Cummins engines (ISB, ISC, ISL, ISX, X12, X15) rely on the Diesel Particulate Filter (DPF) and aftertreatment system to control soot output. Understanding how the regeneration process works — and how to perform a forced regen when needed — helps prevent costly downtime, derates, and unnecessary shop visits.
This guide explains how Cummins regeneration works, how to monitor it, and how to run a forced regen using INSITE or Universal Diagnostics software.
How Cummins Regeneration Works
All modern Cummins engines use the following components to manage soot:
- Diesel Oxidation Catalyst (DOC)
- Diesel Particulate Filter (DPF)
- Select Catalytic Reduction (SCR)
- DEF dosing system
- Temperature and pressure sensors
Soot builds up in the DPF as the engine runs. Regeneration burns that soot into ash using extremely high exhaust temperatures.
Types of Regeneration on Cummins Engines
- Passive Regen – Occurs naturally during high exhaust temperatures while driving.
- Active Regen – ECM injects extra fuel to raise temperatures when passive regen isn’t enough.
- Parked Regen – Driver-initiated using the dash switch.
- Forced Regen – Performed by a diagnostic tool (INSITE or Universal Diagnostics) when soot is too high.
How Often Should Cummins Regenerate?
Cummins regen frequency depends on usage:
- Highway driving: every 300–600 miles
- Mixed driving: every 150–300 miles
- City/idle-heavy driving: every 40–120 miles
Frequent regens indicate an underlying issue that needs diagnostics.
Signs Your Cummins Is Regenerating
- Idle increases to 900–1200 RPM
- Cooling fan runs loudly
- Burning/hot exhaust smell
- Reduced fuel economy temporarily
- DPF or regen indicator light
When Cummins Regeneration Fails
If an active or parked regen fails, the following faults may appear:
- DPF pressure sensor faults
- NOx sensor issues
- EGR flow faults
- Temperature sensor failures
- DEF dosing problems
If the ECM cannot complete regen, the truck may enter derate and require a forced regen through software.
How to Perform a Forced Regen on Cummins Using INSITE
Step 1: Connect to the Truck
- Use Nexiq USB-Link 3 or RP1210 adapter
- Turn key ON → engine OFF
- Open Cummins INSITE
- Connect to ECM
Step 2: Check Fault Codes
Before performing a regen, look for faults that block regeneration such as:
- DPF differential pressure faults
- DOC/DPF temp sensor faults
- EGR rate faults
- NOx sensor faults
- DEF quality or dosing faults
Address or clear these issues before continuing.
Step 3: Navigate to the Regen Menu
In INSITE:
- Go to ECM Diagnostic Tests
- Select Aftertreatment
- Choose DPF Regeneration
Step 4: Start Forced Regen
- Follow the prompts on screen
- Place transmission in neutral
- Apply parking brake
- Ensure coolant temperature meets requirements (often 160–180°F+)
Engine RPM will rise between 1,000–1,500 RPM. Exhaust temps can exceed 1,100°F as the DPF burns soot.
Step 5: Monitor Live Data
- Soot level percentage
- DPF differential pressure
- Exhaust temps pre/post DOC & DPF
- Fuel post-injection rate
If soot level decreases steadily, the forced regen is working correctly.
Step 6: Confirm Completion
Once complete, verify:
- Soot level returned to normal
- No active regen-related fault codes
- DPF pressure is low at idle
How to Perform a Forced Regen Using Universal Diagnostics
If you don’t have INSITE, Universal Diagnostics (included in our laptops) can also run regen:
- Select your vehicle make/model
- Go to Emissions → DPF Regeneration
- Follow guided instructions
- Monitor exhaust temperatures and soot levels
When a Forced Regen Will Not Fix the Issue
Forced regen cannot resolve:
- Clogged or melted DPF
- Bad EGR valve or cooler
- Failed NOx sensor
- DEF pump or doser failures
- Temperature sensor out-of-range
- Severe ash buildup
These issues require diagnostics or DPF cleaning.
How to Prevent Regeneration Problems on Cummins
- Fix EGR and NOx faults as soon as they appear
- Use high-quality diesel & DEF
- Avoid prolonged idling
- Drive at highway speeds weekly
- Monitor soot and regen history regularly
Need Help?
If your Cummins engine won’t regenerate, keeps requesting regens, or enters derate mode, contact us below:
- Phone (Toll Free): (877) 210-3245
- Email: info@truckscanners.com
- Contact Page: https://truckscanners.com/contact/
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Need a laptop that can run forced regens, read soot levels, diagnose EGR/NOx issues, and monitor your entire Cummins aftertreatment system? Shop our fully-loaded kits here:
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