Sunday, February 01, 2015

Mercedes MBE 900 Diesel Engine Emission Code dpf out of range high

This code we're working on is a "DPF out of range high" on a Mercedes MBE 900 Diesel Engine. What triggers this code is a pressure differential between the inlet and outlet of the diesel particulate filter cartridge. In the video you can see the clamps on the outside of the muffler that can be removed allowing the cartridge to be removed for cleaning.

There are several shops in town that will do a cleaning of these cartridges. It's a two step process depending on how badly the blockage is. When using detroit diesel diagnostic software you can go in and see what range the filter is running at. It's 0 to 4 range with four being severe. Once the engine control module detects blockage it will run a regen while the engine is in service.

 In a perfect world that's all the emission system would need to do running regenerations to keep operating without any trouble. The DPF amber dash light illuminates when the regen process is taking place. There is no worries if it flashes on and off indicating a normal function instigated by the engine on board computer.

Mercedes calls the engine computer an MCM (motor control module). When hooked up with the laptop and software the tech can find the code and click on the "troubleshoot code" button at the bottom of the screen. This directs you to a step by step process to check one thing at a time then moving on to the next step. In this case the outlet braided pressure hose that reads outlet exhaust pressure of the filter cartridge has to be removed and tested for blockage.

It could be blocked with soot and ash build up and the best thing to do is replace it. This fault was cured replacing the hose. If it did not help the filter cartridge may be plugged up so a forced regen is a good idea. Eventually over time the filter cartridge needs to be serviced or replaced. Mercedes recommends servicing at 125,000 km or 75,000 miles.

We have 18 of these diesel engines in our fleet and have a good deal of experience which is your basic "hands on" experience that is of course the best teacher.

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