Tracker 4WD L4-1.6L VIN 6 (1998)
Oxygen Sensor: Description and Operation
Heated Oxygen Sensor 2 (HO2S 2) Catalyst Monitor
Catalyst Monitor Heated Oxygen Sensor (HO2S 2)
In order to control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a three-way catalytic converter is used.
The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gases, converting them into
harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The PCM has the ability to monitor this process
using the HO2S 1 and the HO2S 2 heated oxygen sensors.
The HO2S 1 sensor produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the Three-Way Catalytic
(TWC) converter. The HO2S 2 sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the
catalysts ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the HO2S 1 signal will be far more active than that
produced by the HO2S 2 sensor.
In addition to the catalyst monitoring, the HO2S 2 heated oxygen sensor has a limited role in controlling fuel delivery. If the HO2S 2 signal indicates a
high or low oxygen content for an extended period of time while in closed loop, the PCM will adjust the fuel delivery slightly to compensate.
If the oxygen sensor pigtail wiring, the connector or the terminal are damaged, the entire oxygen sensor assembly must be replaced. Do not attempt to
repair the wiring, the connector or the terminals. In order for the sensor to function properly, it must have clean reference air provided to it. This clean
reference air is obtained by way of the oxygen sensor wire(s). Any attempt to repair the wires, the connectors or the terminals could result in the
obstruction of the reference air and thus degrade the oxygen sensor performance.
HO2S Heater
The heated oxygen sensors are used to minimize the amount of time required to begin the closed loop fuel control operation and to allow accurate
catalyst monitoring. The oxygen sensor heater greatly decreases the amount of time required for fuel control sensor HO2S 1 to become active. The
oxygen sensor heater is required by the catalyst monitor sensor HO2S 2 to maintain a sufficiently high temperature. The heater provides accurate
exhaust oxygen content readings further from the engine.
