OBD CodesWhat it means
A diesel particulate filter traps soot from the exhaust. From time to time the car burns the soot off at high temperature, a process called regeneration. These codes mean the filter is too full, is not trapping soot as it should, or the pressure sensor that watches it is faulty.
Codes in this group
| Code | Meaning |
|---|---|
| P2002 | Particulate filter efficiency below limit, bank 1 |
| P2003 | Particulate filter efficiency below limit, bank 2 |
| P242F | Particulate filter restricted by ash |
| P244A | Particulate filter pressure difference too low, bank 1 |
| P244B | Particulate filter pressure difference too high, bank 1 |
| P2452 | Particulate filter pressure sensor A circuit fault |
| P2453 | Particulate filter pressure sensor A reading out of range |
| P2454 | Particulate filter pressure sensor A signal low |
| P2455 | Particulate filter pressure sensor A signal high |
| P2463 | Particulate filter soot build-up too high |
Bank 1 is the side of the engine that has cylinder 1. Sensor 1 is before the catalytic converter and sensor 2 is after it. More terms explained.
What you may notice
- DPF warning light
- Loss of power or limp mode
- Higher fuel use
- Engine fan running after switch-off, or a hot smell, during regeneration
Common causes
Most likely first:
- Mostly short trips, so regeneration never completes
- A faulty or blocked pressure sensor or its small hoses
- Faults elsewhere (EGR, injectors, boost) making extra soot
- The wrong engine oil
- A filter that is full of ash at high distance
What to check first
- If the DPF light comes on and the car drives normally, a steady run of 20 to 30 minutes on an open road often lets it clean itself: follow the owner's manual
- If power is reduced or more lights are on, do not keep driving: a workshop can run a forced regeneration
- Removing the filter is illegal for road use in many countries and makes the car fail emission checks
Have a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.
After the repair
Once the cause is fixed, the code can be cleared with a scan tool, or the warning light goes out by itself after several trips without the fault. Clearing a code without fixing the cause only hides it for a while. More about clearing codes.
Related codes
Exhaust gas recirculation (EGR) (P0400), Secondary air injection (P0410), Catalytic converter efficiency (P0420), Fuel vapour (EVAP) system (P0440), Diesel exhaust fluid (AdBlue) and SCR system (P203F). All codes.
Written in November 2026. These are generic OBD-II codes, the same on all makes. Causes and repair steps differ between models.