The ECM uses an oxygen sensor to ensure the air/fuel ratio is correct for the catalytic converter. Based on the oxygen sensor signal, the ECM will adjust the amount of fuel injected into the intake air stream.
There are different types of oxygen sensors, but two of the more common types are:
• the narrow range oxygen sensor, the oldest style, simply called the oxygen sensor.
• wide range oxygen sensor, the newest style, called the air/fuel ratio (A/F) sensor.
Also used on very limited models in the early 90s, was the Titania oxygen sensor.
OBD II vehicles require two oxygen sensors: one before and one after the catalytic converter. The oxygen sensor, or air/fuel ratio sensor, before the catalytic converter is used by the ECM to adjust the air/fuel ratio. This sensor in OBD II terms is referred to as sensor 1. On V-type engines one sensor will be referred to as Bank I Sensor 1 and the other as Bank 2 Sensor 1. The oxygen sensor after the catalytic converter is used by the ECM primarily to determine catalytic converter efficiency. This sensor is refer-red to as sensor 2. With two catalytic converters, one sensor will be Bank 1 Sensor 2 and the other as Bank 2 Sensor 2.
Oxygen Sensor Construction
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