Signs worth recording
Note power loss, more frequent or interrupted regenerations, higher fuel use, smoke, and warning lights. Record when the issue started and whether it followed a repair, route change, or long periods of idling.
This history and the fault codes help distinguish filter restriction from sensor, temperature, or engine-operation problems.
Why you should not clear codes first
Codes and vehicle data are diagnostic clues. Clearing them before recording them can erase useful information. CARB also warns that clearing codes shortly before a Clean Truck Check OBD test may leave a vehicle with a “Not Ready” result.
Cleaning, regeneration, or repair?
Regeneration converts some soot to ash. Cleaning addresses buildup in a filter that can still be recovered. A damaged filter, failed sensor, or engine fault calls for another repair. Diagnostics help choose the right path rather than replacing parts by guesswork.
If the truck is down, share its symptoms, codes, and location. We can review whether mobile or workshop DPF cleaning is the right next step.