Overview
What the DPF does
Traps soot from the exhaust to keep the tailpipe emissions clean. Without a DPF, diesel cars produce visible soot in city driving. The DPF works on a burn-off cycle: soot accumulates during normal driving, then the DPF heats up (via post-injection) to burn it off.
Passive vs active regeneration
Passive regeneration happens naturally during sustained motorway driving: the exhaust temperature gets high enough on its own to burn the soot. Active regeneration is commanded by the DDE when soot loading reaches a threshold: the DDE runs post-injection to raise the exhaust temperature, the engine runs at a slightly higher RPM, and the burn-off happens over 15–30 minutes.
Why short trips are the problem
Short-trip driving never gets the exhaust hot enough for passive regen. Active regen is supposed to compensate, but if the trip ends before active regen completes, soot loading increases over time. Eventually the DPF warning comes on, and a forced regen or a DPF replacement is the fix.
DPF-related codes
P2002 (DPF efficiency below threshold, Bank 1), P2003 (Bank 2), P2454 (DPF pressure sensor A circuit low), P2463 (DPF restriction, excessive soot accumulation), P04DB (DPF temperature sensor A circuit low). Not all of these are in the public DTC catalog; use the live lookup to check.
Forced regeneration
A forced regen is a write path — the DDE commands post-injection for 15–30 minutes. The car must be outdoors or in a workshop with exhaust extraction. The routine ID is currently unverified per the project audit; cross-check against ISTA before relying on it.
FAQ
What is DPF?
Diesel Particulate Filter. A ceramic filter in the exhaust that traps soot.
How does DPF regeneration work?
The DDE runs post-injection to raise the exhaust temperature, burning off the trapped soot. Passive regen happens during motorway driving; active regen is commanded when soot loading reaches a threshold.
What causes DPF failure?
Mostly short-trip driving that prevents regen. Eventually soot loading reaches the point where the DPF can’t be regenerated and a replacement is the only fix.