The diesel particulate filter differential pressure sensor measures the current pressure differential upstream and downstream of the diesel particulate filter in the exhaust gas stream.
For this purpose, there is a pipe connection upstream and downstream of the particulate filter.
The readings are converted by the diesel particulate filter differential pressure sensor into a voltage signal and signaled to the PCM.
1 Diesel particulate filter
2 Pipe connections โ diesel particulate filter differential pressure sensor
3 Oxidation catalytic converter
The soot particles and ash collected in the diesel particulate filter result in a pressure change of the exhaust gas upstream and downstream of the diesel particulate filter. The altered pressure value due to the soot load is used by the PCM as an input parameter for determining soot load.
If the measured value exceeds the stored maximum value, regeneration of the particulate filter is initiated, taking into account the necessary boundary conditions. In addition, the diesel particulate filter differential pressure sensor is mainly used for fault diagnosis.
Effects of faults
In the event of a fault the engine power output is reduced by the PCM by reducing the injected fuel quantity.
Diagnosis
The monitoring system performs the following checks using the diesel particulate filter differential pressure sensor:
โข Plausibility check,
โข Diesel particulate filter efficiency
โข Diesel particulate filter overloaded,
โข Diesel particulate filter blocked,
โข Monitoring of the maximum regeneration attempts in the lower load range.
The plausibility check is divided into two tests:
โข With the engine running: The differential pressure is measured across the diesel particulate filter. This is determined according to the difference between the anticipated pressure of the exhaust gas stream as calculated by the PCM and the actual pressure of the exhaust gas stream before and after it passes through the particulate filter. This test is performed under certain operating conditions (depending on coolant temperature, engine speed and engine load โ regeneration not activated). Assuming that these conditions are met, the sensor signal must be within the specified limit values.
โข With the engine switched off: Here, the differential pressure is measured before the engine is started or immediately after it has been switched off. If the differential pressure calculated via the diesel particulate filter is greater than the value specified by the PCM, this is recognized as an implausibility.
The diesel particulate filter efficiency test determines whether the filter material in the diesel particulate filter is in sound condition.
The diesel particulate filter element itself poses a certain resistance to the exhaust gas stream that is calculated by the PCM. To achieve the calculated exhaust gas stream, the test is performed under certain operating conditions.
If the value measured here is below the minimum value calculated, the diesel particulate filter is recognized as inefficient.
A diesel particulate filter is recognized as overloaded if the differential pressure across the diesel particulate filter (under certain operating conditions) exceeds the overload limit calculated by the PCM.
A diesel particulate filter is recognized as blocked if the differential pressure across the diesel particulate filter (under certain operating conditions) exceeds the blocking limit calculated by the PCM.
Monitoring of the maximum regeneration attempts in the lower load range: The diesel particulate filter regeneration system is designed to enable regeneration to be performed even under poor conditions (low coolant temperature, engine speed and engine load).
In the worst-case scenario the system may start regeneration attempts but be unable to complete them. These attempts are counted by the PCM. If the maximum number of regeneration attempts is reached, this results in a fault entry the next time the ignition is switched on.
Certain faults lead to increased diesel particulate emissions, with the result that the EOBD limits are exceeded. It is therefore a MIL active component.
Possible diagnostic trouble codes: P2453, P2454, P2455, P2002, P242F, P2458, P2459