WHAT IS DPF
Posted 05 December 2010 - 11:57 PM
The fuel borne diesel particulate filter system consists of the following components:
Diesel particulate filter (DPF)
Pressure differential sensor
Fuel additive system
The DPF reduces the pollution generated by diesel vehicles by filtering soot particles out of the exhaust gases.
Pressure Differential Sensor
The pressure differential sensor monitors the pressure drop within the DPF.
The temperature sensor is incorporated to monitor the temperature within the DPF and sends a signal to the power-train control module (PCM).
Fuel Additive System
The fuel additive system consists of a fuel additive system module and a fuel additive tank with a dosing pump.
Regeneration of the DPF
NOTE: Soot particles can accumulate in the exhaust tailpipe. This is an inherent by-product of the regeneration process and should not be considered a concern.
NOTE: During regeneration it is possible that white smoke may be emitted from the exhaust tailpipe. This is an inherent by-product of the regeneration process and should not be considered a concern.
The pressure differential sensor is connected to the DPF by the pressure differential sensor lines to monitor the pre-pressure and post-pressure of the DPF. The pressure differential sensor converts these measurements to a signal voltage, which is then sent to the PCM to be used as part of the decision of whether to apply the regeneration process or not.
The PCM will choose the optimum time for the regeneration of the DPF. Under normal operating conditions the regeneration process occurs when the PCM has calculated that the DPF requires regeneration and that predetermined vehicle conditions are met (for example, coolant temperature, vehicle speed and engine load).
The engine management system will then close the exhaust gas recirculation (EGR) valve and actuate the turbocharger. This will then generate more engine load and the exhaust gas velocity is reduced. Then, with the aid of the fuel additive and post injection, the soot particles are burnt.
Following regeneration there is an ash residue left in the DPF. Due to this ash residue the DPF must be serviced every 120,000 km.
Manual regeneration of the DPF
If the DPF becomes blocked the pressure differential sensor will register a high pressure diagnostic trouble code (DTC) with the PCM, the malfunction indicator lamp (MIL) will be illuminated and the limp home mode activated.
A blocked DPF can be a result of:
Excessive soot particles production
Multiple failed regeneration events
Mechanical or electrical failure of a related system or sub-system (for example, EGR valve stuck open, charge air system leak, fuel injectors)
The manual regeneration of the DPF can be used to clear the soot particles from the DPF.