W18.40-1034-06
Location
B604 Oil pressure sensor
The oil pressure sensor (B604) is screwed on below the coolant pump into the crankcase.
Task
The oil pressure sensor (B604) enables the engine management (MCM) control unit (A4) to determine the current engine oil pressure.
W18.40-1029-01
Design
1 Sensor element
2 Sensor membrane
3 Hybrid element
B604 Oil pressure sensor
Function
The engine oil pressure operates on the sensor element (1) of the hybrid element (3) and distorts the sensor membrane (2).
There are four pressure-dependent resistances (strain measuring resistors) on the sensor membrane (2). Its bridge circuit is supplied with voltage by an electronic analysis system which also serves for signal amplification and signal correction. The electronic analysis system is powered by the engine management (MCM) control unit (A4) with 5 V direct voltage.
The resistors in the sensor membrane (2) are arranged in such a way that on deforming the sensor membrane (2) two resistors are clinched and two resistors elongated.
Contraction and elongation changes the electrical resistance of the resistors which in turn has effects upon the measurement voltage, which is being applied to the electronic analysis system.
The electronic analysis system amplifies the measurement voltage, compensating for possible temperature fluctuations or balancing out possible manufacturing tolerances on the resistances and passes on the cleared out measurement voltage to the engine management (MCM) control unit (A4) which uses it to derive the current engine oil pressure.