P242F
Diesel Particulate Filter Restriction - Ash Accumulation
High· Fix promptlyProfessionalPowertrainGeneric, all makes
What it means
The DPF is clogged with ash. Unlike soot, ash cannot be burned off by regeneration; it builds up slowly over the life of the filter from oil additives.
Is it safe to drive?
Drivable for now, but expect limp mode. Plan to clean or replace the DPF.
Symptoms
- DPF warning light
- Reduced power
- Frequent regenerations
Probable causes
Most likely first
- 1High mileage on the DPF
- 2Engine burning oil
- 3Wrong oil (not low-ash)
How to diagnose it
Work through these in order before buying parts
- 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
- 2Check the ash load value on live data.
- 3Check for oil consumption.
- 4Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.
Common fixes
- Professional off-car DPF cleaning
- Replace the DPF and reset the ash counter
This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.