P242F Diesel Particulate Filter Restriction – Ash Accumulation
OBD-II Trouble Code Technical Description
Diesel Particulate Filter Restriction – Ash Accumulation
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to most newer diesel vehicles (Ford, Mercedes Benz, Vauxhall, Mazda, Jeep, etc.). Although generic, the specific repair steps may vary depending on make/model.
On rare occasions, when I have discovered a stored P242F code, it has meant that the powertrain control module (PCM) has detected a level of ash restriction in the diesel particulate filter (DPF) deemed to be restrictive. This code is used exclusively in diesel powered vehicles.
The DPF looks like a muffler or catalytic converter that is protected by a steel, inline exhaust housing. It is located ahead of the catalytic converter and/or the NOx trap. Large soot particles are trapped in the DPF element. Small particles and other (exhaust gas) compounds are allowed to pass through.
The most important part of any DPF is the filtration element. The DPF can be constructed using one of several elemental compounds that trap soot and still allow engine exhaust to pass through. They include paper, metal fibers, ceramic fibers, silicone wall fibers, and cordierite wall fibers. Cordierite is one type of ceramic based filtration compound and the most common type of fiber used in DPF applications. It is inexpensive to manufacture and possesses exceptional filtration characteristics.
As exhaust passes through the element, large particles of soot are trapped between the fibers. When sufficient soot is accumulated, exhaust pressure increases accordingly and the filtration element must be regenerated in order to allow spent exhaust gases to continue flowing through.
Ash accumulation is a side effect of DPF filtration and regeneration. It is caused by the extended use of incombustible materials like lubricant additives, trace elements in diesel fuel/additives, as well as debris from engine wear and corrosion. Ash typically accumulates along the DPF walls or in plugs near the rear of the filtration element. This significantly decreases the effectiveness of the filtration element and dramatically reduces the filter’s soot storage arrangement and capacity.
Because the ash is situated near the walls and rear of the DPF, soot particles are forced to the front, effectively reducing channel diameter and filter length. This can result in increased flow velocity (through the DPF) and a resultant increase in the output signal voltage of the DPF pressure sensor.
When the PCM detects these notable variations in DPF flow, velocity, or volume, a code P242F will be stored and a malfunction indicator lamp (MIL) may be illuminated.
Severity & Symptoms
The conditions for causing the code P242F to be stored may cause internal engine or fuel system damage and should be addressed with haste.
Symptoms of a P242F code may include:
Causes
Possible causes for this engine code include:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
A diagnostic scanner, a digital volt/ohmmeter, and a reliable vehicle information source (I use All Data DIY) will be necessary when diagnosing a code P242F.
I would start a diagnosis of a stored P242F with a visual inspection of related harnesses and connectors. I would focus on wiring that is routed near hot exhaust components and sharp edges (such as exhaust shields). I like to proceed by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. Write this information down for future reference. It may prove helpful if this code proves to be intermittent. Next, I’d clear the codes and test-drive the vehicle.
If the vehicle has been operated using excessive engine additives and fuel system additives, or if the DPF regeneration schedule has been ignored (passive DPF regeneration systems), suspect that ash accumulation is at the root of the condition for this code being stored. Most manufacturers (of modern clean diesel fuel powered vehicles) recommend a maintenance schedule for DPF ash removal. If the vehicle in question is at or near the mileage requirement for DPF ash removal, suspect that ash accumulation is your problem. Consult your vehicle information source for DPF ash removal procedures.
If the code immediately resets, consult the vehicle information source for instructions on testing the DPF pressure sensor using the DVOM. If the sensor does not comply with manufacturer’s resistance specifications, replace it.
If the sensor is good, check for clogs and/or breakage in the DPF pressure sensor supply hoses. Replace hoses as required. High temp silicon hoses must be used for replacement.
If the sensor is functioning properly and supply lines are intact, begin testing system circuits. Disconnect all related control modules prior to testing circuit resistance and/or continuity with the DVOM. Repair or replace open or shorted circuits as required.
Additional diagnostic notes:
Need help?
Let us fix your problem. You are most welcome our diagnosis experts have in most cases the knowledge and skills to find the cause of the error code p242f and to solve the problems.
Make an appointment for diagnosis
"Delete Error Code Permanently, Disable DTC Error Code Function for p242f in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p242f and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p242f.
