Common Aftertreatment System Issues in Diesel Trucks
Solutions for Emissions, Regens, Derates & DEF Failures
At Cali Filtrations, we solve the most costly and frustrating aftertreatment issues in diesel trucks. Whether you’re a fleet manager or an owner‑operator, if your truck is derating, constantly regenerating, or failing emissions tests.
— we’ve got your back.
Common Aftertreatment System Issues in Diesel Trucks
Engine Derate
(5 MPH Limiting)
We’ll diagnose, repair, and restore your truck to full performance.
Common causes include:
- Clogged DPF
- Failed regens
- DEF dosing faults
- Sensor or SCR failures
Excessive Regenerations
We clean, reprogram, and restore full regen function to avoid future failures.
Frequent regens are often caused by:
- Soot buildup in DPF or DOC
- Faulty temp/pressure sensors
- Leaky injectors or low exhaust temps
Check Engine / DEF Warnings
We reset codes and fully restore SCR function.
Typical causes:
- DEF quality or level faults
- NOx sensor errors
- Crystallized DEF injectors or lines
Failed Forced Regen
We service and safely remove/install DPF, DOC, SCR, or One-Box systems.
Causes:
- DPF overfilled
- DOC restriction
- Sensor failure
DEF System Failures
Full DEF flush + reprogramming included.
From “incorrect DEF quality” alerts to full system faults. We repair:
- DEF injectors
- Pumps & tank sensors
- Crystallized lines & clogged filters
CARB Testing & Compliance Services
Is your truck not passing a CARB emissions test?
We offer:
- Official CARB aftertreatment testing
- Repairs and reprogramming to bring trucks into compliance
- Resolution of opacity failures, OBD readiness faults, and DPF-related rejections
We work with fleets and owner-operators to get their vehicles CARB-certified and back on the road—fast.
- Book a Diagnostic Today
We offer fast, expert service for the most common aftertreatment issues.
- In-shop and mobile service
- Same-day diagnostics
- Filter reinstalls & controller reprogramming
- CARB inspections & compliance