DPF — diesel particulate filter clogged
The amber DPF (Diesel Particulate Filter) or FAP icon lights up on diesel cars when soot accumulation exceeds 40–50%. Continued city driving speeds up clogging and ends in a $1500–3000 replacement.
What this indicator means
The DPF is a ceramic exhaust filter that traps soot particles. Passive regeneration (300–500 °C on the motorway) burns soot off automatically. If the vehicle mainly does city runs, exhaust temperature never reaches the threshold and soot accumulates. Active regeneration begins on ECU command — extra fuel is injected to heat the filter to 600 °C.
Common causes
- Predominantly short city trips without warm-up
- Interrupted regeneration (engine shut off mid-cycle)
- Faulty differential pressure sensor (Delta P)
- Injector or rail-pressure issues (incomplete combustion)
- Poor-quality diesel fuel (high sulphur content)
- Exhaust leak upstream of the DPF (cracked manifold)
What to do as a driver
Drive 20–30 minutes on the motorway at 3500–4000 rpm — this triggers active regeneration. Do not shut off the engine immediately on arrival. In the Car Diagnostics app you can see DPF soot load (mode 22, live view). If the light stays on after a highway run, forced regeneration via a service tool or chemical flush is needed.
Safety
Important: without action for a few hundred km the filter clogs to the emergency threshold (75%+), after which only replacement helps.
Related DTC codes
- P2002
- P2452
- P246C