What does P242F mean?
Ash is the part of what the DPF traps that regeneration cannot burn off. It comes mostly from additives in engine oil. Over many miles it builds up. P242F means the computer estimates the ash load is too high.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light and exhaust filter message
- Frequent regens
- Possible derate
Common causes
- High-mileage DPF that has reached its ash limit
- Engine burning oil (adds ash faster)
- Wrong engine oil (use diesel-rated low-ash oil such as API CK-4)
- DPF pressure sensor problem making the estimate wrong
How to diagnose P242F
- Check DPF pressure readings and the ash estimate with a scan tool.
- Check oil consumption.
- Check the DPF pressure sensor and hoses.
How to fix it
- Have the DPF cleaned off-vehicle (ash cannot be burned off)
- Replace the DPF
- Reset the ash learn after cleaning (scan tool)
- Fix oil consumption
Estimated repair cost
Likely repairs for P242F run from about $300 to $7,000, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Diagnostic fee (scan + testing) | $100 - $200 |
| DPF off-vehicle cleaning | $300 - $900 |
| DPF replacement (pickup) | $2,000 - $7,000 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P242F?
Moderate severity
Drivable to the shop. Do not ignore it.
Make-specific notes
Cummins (Ram 6.7L)
P242F is a well-known code on Ram 6.7L trucks. Check the DPF pressure sensor before paying for a DPF.
Always check open recalls and technical service bulletins for your VIN.
P242F FAQ
What does P242F mean?
P242F stands for "Diesel Particulate Filter Restriction - Ash Accumulation". Ash is the part of what the DPF traps that regeneration cannot burn off.
Can I drive with a P242F code?
Drivable to the shop. Do not ignore it.
How much does it cost to fix P242F?
It depends on the cause. The likely repairs for P242F range from about $300 to $7,000 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P242F?
The most common causes are: high-mileage DPF that has reached its ash limit; engine burning oil (adds ash faster); wrong engine oil (use diesel-rated low-ash oil such as API CK-4).