When the Diesel Particulate Filter warning light is flashing, which service action is correct?

• A. Remove DPF for cleaning.
• B. Refill the Urea reservoir.
• C. Perform a manual regeneration.
• D. Run the engine at high idle.

Answer: (C)

When the DPF warning light is flashing, the filter has become heavily loaded with soot and needs to be cleaned through a regeneration cycle. The correct service action is to initiate a manual regeneration. This uses diagnostic tools or the service procedure to raise the exhaust temperature in a controlled way and burn off the accumulated soot, restoring the filter’s efficiency.

Removing the DPF for cleaning isn’t the proper first step, since cleaning should be done through a designed regeneration process and may require specific procedures and equipment. Refill the Urea (AdBlue) reservoir addresses NOx in the exhaust after-treatment system, not the soot buildup in the DPF. Running the engine at high idle might help in some cases, but it’s not a guaranteed or reliable way to perform the necessary regeneration; a manual regeneration ensures the soot is burned off correctly and the system is reset.