In the first article, we described what diagnostic trouble codes (DTCs) are and how they work. We gave practical examples of how to use them to diagnose the exhaust system. Here we will present the most popular examples of DPF error codes related to other failures. In the second part, you can familiarize yourself with error codes related to sensor faults.

P242F – DPF limitation – ash accumulation

Ash in the DPF filter is a product of the use of lubricating additives for engine or diesel oils as well as impurities resulting e.g. from corrosion or general engine wear. It settles in the DPF filter on the walls or in its back, and thus blocks its capacity. The soot can be burned off in the process of automatic regeneration. On the other hand, the ash can only be removed by washing or replacing the DPF.

The P2424F code will be issued in one of the cases:

• actual clogging of the DPF filter – be it ash or unburned other sediments, which in turn indicate ineffective self-regeneration
• the use of engine or diesel oil not adapted to the exhaust system with a DPF filter
• damage to the sensor or its circuits due to their opening or short circuit, breaking of the sensor cables

In addition to the P242F code, the board indicator light (MIL) may also come on.

P2463 – DPF limitation – soot accumulation

Ash is not the only product of combustion. The DPF also accumulates soot, which, fortunately, can be burned during self-regeneration. Its frequency is regulated by a pressure sensor that compares the outlet values with those programmed by the manufacturer. Excessive soot that has not been burned regularly can result in sending code P2463. It may also indicate a malfunction of the regeneration process, a damaged sensor or its wiring.

There may also be other causes, e.g. diesel exhaust oil of poor quality or in insufficient quantity. Ultimately, during the diagnosis, a defect on the computer or its software can be suspected.

Regardless of what has failed, this is one of the most serious mistakes to look at carefully. Otherwise, further damage to the exhaust system or even the engine itself may occur.

P244A – DPF differential pressure too low (Bank 1) / P244B – DPF differential pressure too high (Bank 1)

The outlet pressure sensor in the DPF filter not only has to check its degree of filling. It also detects filter removal or malfunction. When the outlet pressure is too low or the pressure difference too high, the code P244A or B and the MIL lamp are activated. Automatic regeneration is suspended.

Removing the DPF filter is just one of the reasons. The DPF filter and the pressure sensor can be damaged as well. The code will indicate a leak in the sensor cable or an exhaust gas leak before or near it. It also disturbs the pressure value.

P2458 – DPF regeneration time / P2459 – DPF regeneration frequency

During the automatic regeneration of the DPF filter, the exhaust gas temperature increases, which facilitates burning of soot and carbon deposits. In order for it to occur, the engine must maintain increased RPM for min. 15-30 min. However, with urban driving style and too short time at higher revs, self-regeneration is not complete. As a result, the filter is still clogged. As a result, the computer reads the discharge pressure outside the norms.

Incorrect regeneration time can be caused by a defective filter, pressure sensor or short circuit in the electric circuit. Other reasons are bad or too little fuel exhaust fluid. It is also possible that the on-board computer or its software has been damaged.

Regeneration of DPF must take place not only for a limited time, but also with appropriate regularity, guided by the pressure sensor readings. All causes that cause the P2458 error code can also trigger the P2459 code. Self-regeneration usually takes place every 300-600 km, but when it is interrupted, the DPF will not reach sufficient throughput. Therefore, it will have to be repeated more often.

Examples of DPF error codes – summary

Most often, the malfunctions that display the error codes associated with the DPF filter and this section of the exhaust system are associated with a clogged filter or sensor malfunction. When diagnosing, you cannot rule out leaks in the system or short circuits in the electrical circuits. Not even malfunction of the diagnostic computer.

Some of the errors result from the selection of unsuitable or poor quality consumables, e.g. engine or diesel oil, or simply from wear. Some of them are soft code and are canceled after resolution of the cause and subsequent measurement.

The lighting of the DPF indicator on the dashboard should be a sign for any driver who needs a longer ride at increased speed to complete self-regeneration. If this does not help, it is necessary to go to the diagnostic station and read the error codes from the computer.

See also the second part with the codes P0470, P2002, P2003, P2031-36, P2452, P2453, P2454 and P2455.