Introduction to On Board Diagnostics (II)

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Sensors and ActuatorsEmployed in OBD IIDiagnosticsExhaust Gas Oxygen (EGO) sensorThere are two types of EGO sensors, both based on the use of oxides of materials.One uses Zirconia (ZrO 2 ), and the other uses titanium oxide (TiO 2 ). But ZrO 2is most popular and is described here. The sensor consists of ZrO 2 sandwichedbetween two platinum electrodes. One electrode is exposed to exhaust gasin the exhaust manifold, and the other electrode is exposed to normal nair forreference. The electrode that is exposed to exhaust gas is coated d with porous protectiveovercoat.The ZrO 2 attracts oxygen ions and they accumulate on theZrO 2 surface just inside platinum electrode. AS oxygen ions are negativelycharged, there will be a potential across the two electrodes if the oxygen ionson exhaust gas side are less than the oxygen ions on the normal air side. Thepolarity of this voltage is positive on the exhaust gas side and negative on air side.The voltage depends on the concentration of the oxygen in the exhaust gas and theEGO sensor temperature.
Sensors and ActuatorsEmployed in OBD IIDiagnosticsEGO Oxygen sensor:Diagnostics: Check for abrupt change in voltage at stoichiometry. Must haverapid changes of output voltage in response to exhaust gas oxygen changes.Must have large difference in sensor output voltage between rich and leanA/F ratio conditions. Must have stable voltage with respect to exhausttemperature.OBD II DTCsThe failure modes of EGO sensor are diagnosed by OBD II.DTCs for these faults are 400-408..
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Introduction to On BoardDiagnostics
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OBD II monitors more components and
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Powertrain and EmissionControls in
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Powertrain and EmissionControl in P
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OBD II for L & MD VehiclesSTD Manua
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OBD II for L & MD VehiclesDiagnosti
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Fundamentals of PowertrainControl s
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Introduction to On Board Diagnostics (II)

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