Component Description For Egr Differential Pressure Sensor - Mercedes-Benz OM 471 Introduction Into Service Manual

System components
GF14.20>W>1004H
ENGINES 471.9 in MODEL 963, 964
Location
1 Exhaust gas recirculation cooler
2 Exhaust gas recirculation pipe
B621 Exhaust gas recirculation (AGR)
differential pressure sensor
The EGR (AGR) differential pressure sensor
(B621) is located on the front side of the
engine, where it is screwed in from the
outside into the exhaust gas recirculation
pipe (2).
Task
The EGR (AGR) differential pressure sensor
(B621) supplies the engine management
(MCM) control unit (A4) with information in
order to calculate the EGR volumetric flow
rate.
Design
3 Electrical connection
4 High pressure connection
5 Low>pressure connection
6 Seals
7 Bolts
The EGR (AGR) differential pressure sensor (B621) consists of a
plastic housing which it fitted inside with two chambers which is
separated from a thin membrane which functions as a mechanical
intermediate stage. Four strain gauge resistances (DMS) are
located on the membrane in the bridge circuit.
The membrane is exposed on one side to the exhaust and thus the
pressure.
The EGR (AGR) differential pressure sensor (B621) is fitted with an
electronic analysis system and for signal transmission to the engine
management (MCM) control unit (A4) and a power supply due to
the bridge circuit it contains
Function
If the exhaust recycling pipe (2) has exhaust flowing through it
there is a respective pressure applied at the part of the membrane
in the EGR (AGR) differential pressure sensor (B621) exposed to
the exhaust. This is therefore distorted and the strain gauge
resistances (DMS) are elongated or squashed. The strain gauge
resistances (DMS) reacts to the change in length with a change in
its ohmic resistance. These values are prepared by the electronic
analysis system and transmitted as analog signals to the engine
management (MCM) control unit (A4).
156

Component description for EGR differential pressure sensor

– This printout will not be recorded by the update service. Status: 09 / 2011 –
Since the EGR (AGR) differential pressure sensor (B621) has a
constant measuring current flowing through it there is a voltage
drop due to the change in resistance over which the engine
management (MCM) control unit (A4) can deduce the associated
pressure value.
2.8.11
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W14.20>1024>81