P242F fault code: DPF restriction caused by ash
Plain-language definition
Particulate Filter Restriction - Ash Accumulation Bank 1
What does it mean?
On diesel cars, soot particles in the exhaust are trapped in the diesel particulate filter (DPF). The soot that builds up is cleaned out by a process called regeneration, which burns it at high exhaust temperatures. Ash is different: it mostly forms from the additives in the small amount of oil the engine burns, it doesn't burn, and regeneration doesn't clean it out. That's why it builds up slowly over the life of the filter.
P242F is stored when the engine computer calculates that the amount of ash in the filter has reached the allowed limit. How this is calculated varies by car: the engine computer may estimate the amount of ash from data such as the distance driven and the fuel burned, or it may look at a pressure difference that stays high even after a regeneration (the difference between the filter's inlet and outlet). If the engine computer reports these values, the 2dakika report also shows the ash and soot levels in the DPF.
Along with this code, a DPF warning or the check engine light may come on. On some cars engine power may be limited; you may notice less pulling power, more frequent regenerations or higher fuel consumption. Because ash doesn't burn, the filter may need to be cleaned or replaced at a workshop. Clearing the code doesn't fix the fault; if the problem persists, the code comes back.
How serious is it?
It's a Warning-level code; rather than a sudden fault, it usually shows that the filter has reached its service limit. Because built-up ash doesn't go down over time, the situation usually doesn't improve by itself.
Severity is a guide; if the warning light is flashing or you notice symptoms while driving, have the car checked at a workshop.
Common general causes
- Ash that has built up in the filter over time with high mileage (the filter reaching its service limit)
- The engine burning more oil than normal; burned oil leaves more ash
- Using an unsuitable engine oil instead of the low-ash (low SAPS) oil recommended for cars with a DPF
- On some cars, the filter looking fuller than it really is because of a problem with the differential pressure sensor or its hoses
- The ash value in the engine computer not having been updated at the workshop, even though the filter was cleaned or replaced
The list shows general causes; a workshop finds the actual cause on your car with a check.
Definitions by make
Some manufacturers record the same code under their own wording:
- Isuzu
- Diesel particulate filter restriction detected
Related codes
How does it appear in the 2dakika report?
Particulate Filter Restriction - Ash Accumulation Bank 1
If the code is read as a confirmed (stored) fault, the report shows it with the "Warning" severity; in pending or past records, codes that don't request the warning light and aren't critical appear as "Info". If the engine computer stored them, the conditions when the fault was recorded (engine temperature, rpm, speed) are shown too.
Read this code with the OBD-X1, and clear it from the app after the repair.
Clearing the code doesn't fix the fault; if the problem persists, the code comes back.