Exhaust gas recirculation differential pressure sensor, component description

W14.20-1023-76

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.

W14.20-1024-81

Design

3 Electrical connection

4 High pressure connection

5 Low-pressure connection

6 Seals

7 Screw/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.

For signal transmission to the engine management (MCM) control unit (A4) the ARF (EGR) differential pressure sensor (B621) is fitted with an electronic analysis system and also a power supply due to the installed bridge circuit.

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).

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.