Which of the following best describes what occurs during a passive regeneration of a typical DPF filter?

• A. Usually occurs during normal driving
• B. Requires fuel dosing in the exhaust
• C. Requires spark ignition
• D. May require the driver to pull off the highway

Answer: (A)

Passive regeneration happens automatically when the exhaust heat is high enough during normal driving, so the soot in the diesel particulate filter is burned off by the catalyst without any extra intervention. Because it relies on the heat from regular driving to sustain the oxidation of soot, it doesn’t need fuel dosing into the exhaust, spark ignition, or any special driver action like pulling off the highway. Highway or steady cruising often helps reach and maintain the necessary temperatures, but no explicit driver steps are required for this regen mode.