Service Manuals, User Guides, Schematic Diagrams or docs for : . Car Manuals Subaru Impreza 2001-2002.2004-2007 Approved Subaru Impreza 2004 WRX STi 08. MECHANISM AND FUNCTION 12. FUEL INJECTION (FUEL SYSTEM) 04. Sensors and Switches
<< Back | HomeMost service manuals and schematics are PDF files, so You will need Adobre Acrobat Reader to view : Acrobat Download Some of the files are DjVu format. Readers and resources available here : DjVu Resources
For the compressed files, most common are zip and rar. Please, extract files with Your favorite compression software ( WinZip, WinRAR ... ) before viewing. If a document has multiple parts, You should download all, before extracting.
Good luck. Repair on Your own risk. Make sure You know what You are doing.
Image preview - the first page of the document
>> Download 04. Sensors and Switches documenatation <<
Text preview - extract from the document
W1860BE.book Page 18 Tuesday, January 28, 2003 11:01 PM
SENSORS AND SWITCHES
FUEL INJECTION (FUEL SYSTEM)
4. Sensors and Switches
A: FRONT OXYGEN (A/F) SENSOR
The front oxygen (A/F) sensor uses zirconium oxide (ZrO2) which is a solid electrolyte, at portions
exposed to exhaust gas.
The zirconium oxide has the property of generating electromotive force when its both sides are
exposed to oxygen ions of different concentration and the magnitude of this electromotive force de-
pends on how much the difference is.
The front oxygen (A/F) sensor detects the amount of oxygen in exhaust gases by making use of this
property of the zirconium oxide material.
The zirconium oxide material is formed into a closed end tube and its external surface is exposed
to exhaust gases with smaller oxygen ion concentration, whereas its internal surface is exposed to
atmospheric air. The external surface has a porous platinum coating. The sensor housing is ground-
ed to the exhaust pipe and the inside is connected to the ECM through the harness to be able to
use the current output from the sensor.
The sensor incorporates a ceramic heater to improve its performance at low temperatures.
(4)
(2)
(1)
(3)
FU-00352
(1) Protection tube
(2) Gasket
(3) Sensor housing
(4) Ceramic heater
FU(H4DOTC)-18
W1860BE.book Page 19 Tuesday, January 28, 2003 11:01 PM
SENSORS AND SWITCHES
FUEL INJECTION (FUEL SYSTEM)
When rich air-fuel mixture is burnt in the cylinder, the oxygen in the exhaust gases is almost com-
pletely used in the catalytic reaction by the platinum coating on the external surface of the zirconia
tube. This results in a very large difference in the oxygen ion concentration between the inside and
outside of the tube, and the electromotive force generated is large.
When a lean air-fuel mixture is burnt in the cylinder, relatively large amount of oxygen remains in
the exhaust gases even after the catalytic action, and this results in a small difference in the oxygen
ion concentration between the tube's internal and external surfaces. The electromotive force in this
case is very small.
The difference in oxygen concentration changes drastically in the vicinity of the stoichiometric air-
fuel ratio, and hence the change in the electromotive force is also large. By using this information,
the ECM can determine the air-fuel ratio of the supplied mixture easily. The front oxygen (A/F) sen-
sor does not generate much electromotive force when the temperature is low. The output charac-
teristics of the sensor stabilize at a temperature of approximately 700◦ Jabse Service Manual Search 2026 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo