Mercedes-Benz OM 471 Introduction Into Service Manual page 135

System components
GF49.20>W>3001H
ENGINES 471.9 in MODEL 963, 964 with CODE (M5Z) Engine version Euro VI
Location
1 Exhaust aftertreatment unit:
2 Pressure line
B37 Exhaust pressure sensor, upstream of
diesel oxidation catalytic converter
The exhaust pressure sensor upstream of
the diesel oxidation catalytic converter
(B37) is screwed into the deflection
chamber from the outside, upstream of the
diesel oxidation catalytic converter (DOC).
Task
The exhaust pressure sensor upstream of
the diesel oxidation catalytic converter
(B37) records the pressure at the defined
measuring point in the deflection chamber.
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.
132
Exhaust pressure sensor upstream of diesel oxidation catalytic converter,
component description
– This printout will not be recorded by the update service. Status: 09 / 2011 –
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.
20.7.11
W14.40>1577>76