Location
The exhaust gas aftertreatment unit differential pressure sensor is located on the side of the exhaust gas aftertreatment unit (1) that points towards the vehicle center. The pressure lines (2, 3) connected to it are positioned so that they record the exhaust gas pressure upstream of the diesel oxidation catalytic converter and downstream of the diesel particulate filter at two measuring points.
1 | Exhaust aftertreatment unit |
2 | Pressure line (downstream of the diesel particulate filter) |
3 | Pressure line (upstream of the diesel oxidation catalytic converter) |
B192a | Exhaust gas aftertreatment unit differential pressure sensor |
W49.20-A044-76
Task
The exhaust gas aftertreatment unit differential pressure sensor delivers the values on the differential pressure ratios that prevail in the exhaust gas aftertreatment unit (1) upstream of the diesel oxidation catalytic converter and downstream of the diesel particulate filter to the aftertreatment control module (ACM 3.0) (A60a) based on which it can calculate the volumetric efficiency of the diesel particulate filter.
Structure
The exhaust gas aftertreatment unit differential pressure sensor consists of a piezoresistive pressure sensor element, electronics for signal amplification and a temperature compensation. All components are integrated together on a silicon chip. The silicon chip is protected from corrosion by a protective gel and is cast in a plastic housing.
Via the two pressure connections (4, 5), the pressure sensor element is exposed to the exhaust gas pressure of the two measuring points upstream of the diesel oxidation catalytic converter and downstream of the diesel particulate filter.
4 | Pressure connection (for pressure line upstream of diesel oxidation catalytic converter) |
5 | Pressure connection (for pressure line downstream of diesel particulate filter) |
6 | Electrical connection |
7 | Pressure line (flexible) |
8 | Pressure line (flexible) |
B192a | Exhaust gas aftertreatment unit differential pressure sensor |
W49.20-A015-81
Function
The pressure differential between the exhaust gas pressures upstream of the diesel oxidation catalytic converter and downstream of the diesel oxidation catalytic converter has an effect on the piezoresistive pressure sensor element. This generates a voltage that is amplified by the integrated silicon chip and is forwarded as a voltage signal to the aftertreatment control module.
Because a constant measuring current flows through the exhaust gas aftertreatment unit differential pressure sensor, a voltage drop occurs due to the resistance variation via which the aftertreatment control module can derive the associated pressure differential and thus the current volumetric efficiency of the diesel particulate filter.