System Description

DESCRIPTION
The heated oxygen sensor senses the oxygen concentration in exhaust gas, converts it into a voltage which is sent to the engine control module. The oxygen sensor outputs about 1.0 volt when the air fuel ratio is richer than the theoretical ratio and outputs about 0.0 volts when the ratio is leaner (higher oxygen concentration in exhaust gas.).

The engine control module controls the fuel injection ratio based on this signal so that the air fuel ratio is maintained at the theoretical ratio. The oxygen sensor has a heater element which ensures the sensor performance during all driving conditions.

TROUBLESHOOTING HINTS
1. If the heated oxygen sensor is defective abnormally high emissions may occur.
2. If the heated oxygen sensor check has resulted normal but the sensor output voltage is out of specifications, check for the following items related to air fuel ratio control system.
- Faulty injector.
- Air leaks in the intake manifold.
- Faulty volume air flow sensor, intake air temperature sensor, barometric pressure sensor, engine coolant.