During diesel particulate filter (DPF) regeneration, which parameter should be monitored to assess progress?

• A. Oil viscosity.
• B. Cab temperature.
• C. Tire tread depth.
• D. Exhaust temperature.

Answer: (D)

Regeneration relies on heating the exhaust to a level that burns off the soot trapped in the filter. The exhaust temperature is the best indicator of progress because it directly reflects whether that heat is being achieved and maintained. When regeneration starts, the exhaust temperature rises; it stays elevated as soot is oxidized, and then drops back toward normal once the cycle completes. If the temperature doesn’t rise as expected, regeneration isn’t progressing properly, signaling a potential issue with the system.

Oil viscosity, cabin temperature, and tire tread depth don’t relate to the soot-burning process in the DPF, so they don’t inform you about regeneration progress.