P242F Diesel Particulate Filter Restriction - Ash Accumulation

Description and meaning of DTC p242f

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.

p242f diagnostic trouble code 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: Diminished engine performance Excessive black smoke from the exhaust Higher engine temperatures Higher transmission temperatures

DTC p242f - possible causes

Possible causes for this engine code include: Excessive ash accumulation in the DPF Defective DPF pressure sensor Clogged DPF pressure sensor tubes/hoses Open or shorted circuit/s in the DPF pressure sensor circuit Inefficient DPF regeneration Overuse of engine and/or fuel system additives

How to fix OBD-II diagnostic trouble code p242f

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: Following manufacturer’s DPF ash removal intervals and procedures are critical to DPF efficiency If DPF pressure sensor hoses are melted or cracked, they may need to be rerouted after replacement Consult your vehicle information source to see whether your vehicle is equipped with an active DPF regeneration system or a passive system Clogged sensor ports and clogged sensor tubes are common

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