Mercedes-Benz OM 471 Introduction Into Service Manual page 136

GF49.20>W>3002H
ENGINES 471.9 in MODEL 963, 964 with CODE (M5Z) Engine version Euro VI
Location
1 Exhaust aftertreatment unit:
2 Pressure line
B38 Exhaust pressure sensor
downstream of diesel particulate
filter
The exhaust pressure sensor downstream of
the diesel particulate filter (B38) is screwed
into the deflection chamber from the
outside, downstream of the diesel
particulate filter (DPF).
Task
The exhaust aftertreatment control unit
(ACM) (A60) records the pressure at the
defined measuring point in the deflection
chamber via the exhaust pressure sensor
downstream of the diesel particulate filter
(B38).
Design
Inside the stainless steel sensor housing there is a basic unit to
which two electrodes are attached.
The inner electrode is the measuring electrode, and the outer
electrode is the reference electrode. Above this, exposed to the
exhaust pressure, there is a pressure>sensitive ceramic membrane,
the shared counter>electrode.
Together, this configuration constitutes a plate capacitor. Since
the measuring principle is based on the capacity change, which is
extremely small, the sensor has processing electronics that are
extremely sensitive.
i Introduction of engine OM 471 and exhaust aftertreatment > 09/2011 >
Exhaust pressure sensor downstream of diesel particulate filter, component
description
– This printout will not be recorded by the update service. Status: 09 / 2011 –
System components
Function
The exhaust flowing past the probe deforms the membrane
because of its pressure. The deformation changes the distance
between the capacitor plates and therefore the capacity of the
capacitor. The integrated circuit converts the capacity change
signal into a defined voltage, from which the exhaust
aftertreatment control unit (ACM) (A60) calculates the exhaust
pressure level.
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