Vehicles from model year 2008
Vehicles from model year 2008 are equipped with a diesel particulate filter (DPF), which traps the particulate matter generated during the combustion process and reduces particulate matter emissions to the atmosphere.
The DPF is located in the exhaust system, behind the catalytic converter. The main characteristic of the DPF is its ability to regenerate. Regeneration is the combustion of solid particles trapped in the filter, which prevents blockage of the filter and allows the free passage of exhaust gases. The regeneration process is controlled by the ECM and occurs at calculated intervals and is invisible to the vehicle driver.
For detailed information on the DPF and regeneration processes, please refer to the relevant section of the exhaust system description. For more information refer to Exhaust System (309-00C)
Regeneration plays a very important role, since an overfilled filter can cause engine damage due to excessively high exhaust back pressure, and the filter itself can break or be destroyed.
Exhaust gas and DPF temperatures are controlled by the DPF software in the ECM. The DPF software monitors DPF load based on driving style, distance traveled, and signals from differential pressure sensors and temperature sensors located in the exhaust system upstream and downstream of the DPF. When the predetermined level of solids volume is reached, the DPF is actively regenerated. It is carried out in cooperation with the ECM through the regulation of various engine management functions, such as:
- fuel injection
- intake air flow control with throttle
- EGR
- boost pressure control
The ECM contains the DPF software that manages and monitors the DPF and regeneration processes. The software is broken down into three separate modules: DPF control module, DPF fuel flow control module and DPF air flow control module. These modules interact with each other to provide precise control of the DPF.
These three modules are controlled by a fourth software module, which is called the DPF matching module. The matching module controls the operation of other modules when an active regeneration is requested. The DPF control module is a subsystem of the DPF matching module.
DPF matching module
The DPF coordinating module, upon receiving a regeneration request from the control module, initiates and controls the following DPF regeneration requests:
- Disable EGR
- Boost pressure control
- Increased engine load
- Manifold air pressure and temperature control
- Fuel injection control
NOTE: The EGR valve is open at idle to reduce NO emissions. EGR is not used at partial load due to intake manifold contamination.
When the EGR valve closes, the coordinating module initiates a request for an increase in engine load by controlling intake air temperature and pressure.
After receiving confirmation that intake conditions are under control or that the calibration time has elapsed, the matching module goes into a state of waiting for the driver to release the accelerator pedal. If this happens or the calibration time expires, the matching module generates a request for fuel injection control to increase the exhaust gas temperature.
DPF Fuel Control Module
The DPF fuel management module controls the following functions:
- Synchronization of four separate injections per working stroke and the amount of fuel injected (preliminary, main and two additional injections).
- Injection pressure and switching between three different levels of injection calibration.
In addition to measuring catalyst activity and DPF, controlled injection determines the required injection level. The fuel management system calculates the amount of fuel and the timing of four separate injections for each of the three levels of injection pressure calibration, and controls the switching between levels.
Two additional injections are required to separate the functions of increasing the temperature of the gases in the cylinder and producing hydrocarbons. The first post-injection is used to generate a higher temperature of the gases in the cylinders at the same time as maintaining the same engine torque as in normal (not during regeneration) engine operation. The second post-injection is used to generate hydrocarbons by directing unburned fuel to the catalytic converter without increasing engine torque.
DPF air flow control module
The DPF air flow control module controls the following functions:
- EGR control system
- boost pressure control system
- Intake air temperature and pressure control system
Air intake restriction during regeneration The DPF has the following functions:
- Increasing engine load
- Slower combustion
- Air mass reduction
- Reducing the speed of the exhaust gas and thus increasing the time during which the exhaust gas is in the catalytic converter
DPF temperature sensors
The DPF system uses three temperature sensors. One is located in the turbocharger outlet pipe, the second sensor is located after the catalytic converter, and the third sensor is located after the DPF.
The sensors measure the exhaust gas temperature at the outlet of the turbocharger, before passing through the DPF and after passing through the DPF, and provide the information the ECM needs to calculate the DPF temperature. This information is used in conjunction with other data to calculate accumulated particulate matter and to control DPF temperature.
The sensors are NTC resistors that measure the flue gas temperature. The resistance and therefore the voltage across the sensor decrease as the exhaust gas temperature rises.
In the event of a temperature sensor failure, the ECM uses a substitute value of 350°C.
Differential pressure sensor
Item name | Spare part number | Description |
1 | Low pressure connection | |
2 | High pressure connection | |
3 | electrical connector |
The differential pressure sensor is mounted on the rear of the transfer case, next to the DPF.
The differential pressure sensor is used by the software to monitor the status of the DPF. The two pipes on the sensor are connected by pipes to the inlet and outlet side of the DPF. The tubes allow the sensor to measure intake and exhaust DPF pressure.
As the amount of particulate matter captured by the DPF increases, the pressure on the intake side of the DPF increases compared to the exhaust side. The DPF software uses this comparison in combination with other data to calculate the accumulated number of trapped particles.
By measuring the pressure difference between the DPF inlet and outlet and the DPF temperature, the DPF software can determine if the DPF is clogged and needs to be regenerated.
The DPF is considered overloaded if, under certain operating conditions, the differential pressure exceeds the overload limit calculated by the ECM. The DPF software may attempt regeneration but cannot complete it. These attempts are counted by the ECM and if the maximum number of regeneration attempts is reached, a fault message is stored in the ECM during the next ignition cycle.
The DPF software performs the following checks using the DPF differential pressure sensor:
- Plausibility check
- Checking the efficiency of the particulate filter
- Diesel particulate filter overload check
- Checking for clogged particulate filter
- Control of the maximum number of regeneration attempts in the low load range
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