Barometric Pressure Sensor: Description and Operation

With CODE (494a) USA Version

Engine 113.943 as of 6/1/00

Design:

Pressure sensor position
- Engine 111 EVO EURO3/4

Purpose
- Detecting the absolute pressure in the intake manifold
- The pressure information is required for:
- Function chain check OBD and EURO3/4 (e.g. camshaft adjustment, exhaust gas recirculation or (USA) leaktightness of evaporative emission control system)
- ME2.8: altitude recognition for start enrichment
- Engine 113.960 with code 479: test of cylinder shutoff

Function
The pressure in the intake manifold alters the shape of a diaphragm and the piezo resistors alter their resistance. The output voltage which is influenced as a result of this, is used by the ME-SFI control module as information regarding the pressure in the intake manifold