Rio Cinco L4-1.6L DOHC 16V (2003)
Oxygen Sensor: Description and Operation
HO2 (Oxygen) sensor
Two heated O2 Sensors are used in the vehicle. The sensors produce voltages from 0 to 1 volt, depending upon the oxygen content of the exhaust has in
the exhaust manifold. When a large amount of oxygen is present (caused by a lean air/fuel mixture), the sensors produce a low voltage. When there is a
lesser amount (rich air/fuel mixture) the sensors produce a higher voltage. By monitoring the oxygen content and converting it to electrical voltage, the
sensors act as a rich-lean switch.
Both HO(2) Sensors are equipped with a heating element that keeps the sensors at proper operating temperature during all modes of operation.
maintaining correct sensor temperature at all times allows the system to enter into closed loop operation faster and allows the system to remain in closed
loop during periods of extended idle.
Front HO2 sensor
The front (upstream) HO2 Sensor is located in the exhaust down pipe after the TWC and provides an input voltage to the ECM. The input tells the ECM
the oxygen content of the exhaust gas. The ECM uses this information to fine tune the air/fuel ratio by adjusting injector pulse width.
Rear HO2 sensor
The rear (downstream) HO2 Sensor is located near the outlet end of the catalytic convertor. The rear HO2 Sensor input is used to detect catalytic
convertor deterioration. As the convertor deteriorates, the input from the downstream sensor begins to match the upstream sensor input except for a slight
time delay. By comparing the rear HO2 Sensor input to the input from the front sensor, the ECM calculates catalytic convertor efficiency.
