It is known that the diesel engine is highly economical, and in the presence of the diesel particulate filter is also ecological. Unfortunately, like any filter, diesel particulate filter (DPF) can clog up. On the vehicle Ford Focus, as well as on other models was implemented scheme of automatic periodic burning of the accumulated soot in the filter. The engine control module monitors the changes in the differential pressure of the exhaust gases in the filter indirectly assessing the degree of filter clogging, and when it reaches a certain threshold, a regeneration cycle starts. During regeneration cycle the exhaust temperature increases up to above 500°C, at which the accumulated soot is burning, leaving a much smaller amount of non-combustible ash. Sooner or later, the filter will be filled with ash. Ford recommends the replacing the diesel particulate filter to a new one at 120000 km. When owner finds out the price of a new filter, his mood deteriorates significantly. In fact, the speed of particulate filter ash clogging depends on many factors such as the quality of the fuel and oil, good condition of fuel system components, as well as the nature of vehicle operation. Long high speed trips extend filter life, but short slow ones significantly reduce it. Sometime the engine control module determines that the filter is clogged with ash. In this case, the fault indicator illuminates, and the PCM story fault code P242F - Clogging the diesel particle filter - the accumulation of ash. The car will be in the mode of LOS. In fact, the filter may still be particularly filled with soot, which is not burned out by repeated unsuccessful attempts of regeneration. Optimal for the regeneration is a continuous movement of the car at speeds of over 100km/h. If the car is regularly used for short trips at low speed, the exhaust gas temperature does not reach the optimum value and regeneration will be not completed. Then you can try to do static regeneration. This feature is available in FORScan. However, in some cases, the engine control module refuses to start of static regeneration (probably, considering that the filter is clogged with ash and it did not help). I happened to meet the fault code P242F paired with P2458 (duration of regeneration of the diesel particulate filter) three years ago at 76000km mileage. Unfortunately, at that period there was not so remarkable program as FORScan, and I did not fullfil more detailed diagnosis. I had to go to Ford's company service. They offered to try a static regeneration. I left my car, and when I came to pick up, I received a bill for the replacement of the EGR valve + static regeneration. However, they additionally updated the firmware of the control module. Unfortunately I do not know if the EGR valve was indeed faulty. It is known, that this is a common cause, but no fault codes associated with the EGR was found in memory, and the car was mainly used for short trips. In fact, the filter may still be partially filled with soot, which is not burned out by repeated unsuccessful attempts to regenerate. Unfortunately, a few months ago the problem was repeated with the same error code with mileage of 97000km. This time I become a possibility to use the program FORScan and analyze data from several sensors. According to oscillograms, the EGR valve looked to be OK, and the differential pressure in the DPF exceeded 16kPa at speed 90km/h. It is clear that the absolute values of pressure at different cars may vary, but the engine control module compares first ones with the gauge recorded at the beginning of operation. I attempted to carry out a static regeneration using FORScan. Unfortunately, the engine control module refused to start the regeneration cycle, probably assuming that the filter completely clogged by ash and regeneration is not possible. Then I tried to reset the fault code and to carry out the passive regeneration on the highway. It should be noted that the fault code P242F can not be easy erased. The solution was found in a German forum. The advice was the following: "Pull the plug of the air flow sensor, and then start the engine again, stop the engine, read again the fault codes from memory ..... Now you find 2 additional errors from the MAF sensor. Reconnect plug of the MAF sensor and clear the fault memory ...... now it is possible to erase the P242F together with 2 MAF errors, and the display will not more indicate the engine management system failure." Indeed, the trick with disconnecting of the MAF plug (mass air flow sensor) allowed me to erase the fault code P242F, turn off the fault indication on the dashboard and exit the LOS mode. However, an attempt to carry out the passive regeneration on the highway also failed. Once the vehicle speed exceeds 100 km/h, and the differential pressure in the DPF exceeds 15kPa, PCM showed again the fault code P242F and car activated the LOS mode. Then I have tried to reset the diesel particulate filter learned values using FORScan. The procedure has passed successful, but the fault code P242F was not erased and the system remained in the LOS mode. The procedure has reseted parameters DIST_REGEN and DIS_ASHFULL to 1km and 99999km, respectively. I repeated the trick with a MAF plug, again erased all fault codes and tried to drive a few kilometers. Again, at 100 km/h PCM showed the fault code P242F and the car activated the LOS mode. Then it was decided try to demount the filter and wash it with water. In various forums you can find information about the successful experience of such operations. I should note that the demounting of the filter requires strong nerves, durable tool and one assistant. The most difficult in my case was to unscrew "welded" nuts holding the DPF on the exhaust bellows. Nuts are looking up, and there is very little space. I had to remove the grille under the "wipers" and operated from the top, using two extensions and universal joint for socket wrench plus long tube to create a leverage. Demounted filter was carefully washed with water from a garden hose. In flowing water were observed two factions - black and red (probably soot and ash). It was also noted that at the end of the washing operation the water began to pass through the filter much easier. However, it is almost impossible to remove all excess water from the filter. Therefore, after you install the filter in the car, water must be evaporated. In my case at first the differential pressure jumped up to 10 kPa at idle. However, as expected, the reason for this was the remaining water in the filter. After a short slow trip (see. Graph) the water has completely evaporated from the filter and the pressure has fallen sharply.
I have repeated the trick with a MAF plug and erased all fault codes using FORScan again. Then I once more reseted the diesel particulate filter learned values using FORScan. Subsequent test drive at speeds up to 120 km/h showed a maximum differential pressure of up to 4 kPa. Considering that before washing already at 90 km/h, the pressure reached 16 kPa, then the result is positive. At the time of this writing, the car went after DPF washing about 1800km with an almost continuous sensors data logging. During this time, the car executed 7 regeneration cycles. Differential pressure during this period did not exceed 6.5 kPa (65 hPa) at speeds up to 140km/h. The data showed that the engine control module often starts the regeneration at the most inopportune moment while driving in the city or before the end of the trip. This leads to a significant reduction mileage until the next regeneration (see. Graph).
I would be glad if the experience described here can help to solve the similar problems.