If a customer complains about the above problem, this could be caused by dirt in the dosing unit. There may also be complaints of difficulty starting or the engine stalling. When reading out the error code you may find code P0190 (ramp pressure out of range). In this case, proceed as follows:
1. Use a diagnostic test device to check the ramp pressures via the menu items “Engine” and “Parameters and Measurements”.
2. If the actual value is different from the setpoint value this is more than likely to be due to dirt in the dosing unit. Particles larger than 0.3mm can already give rise to this fault.
3. In this case you will need to replace the dosing unit (see Fig.).
The dosing unit is available as a replacement part, so you do not need to replace the entire high-pressure pump. The unit is extremely susceptible to dirt, so you should take care to avoid any contamination while performing the repair.
Important safety note