Accent GS Coupe L4-1495cc 1.5L SOHC MFI (1999)
Oxygen Sensor: Description and Operation
OXYGEN SENSOR
The Engine Control Module (ECM) uses the oxygen sensor signals to maintain the air fuel mixture at the ratio resulting in optimum fuel economy and
reduced emissions.
The amount of oxygen in the exhaust gases indicates to the front oxygen sensor, whether the air fuel mixture being supplied to the engine cylinders is
rich or lean.
The readings of the rear oxygen sensor are used to indicate the efficiency of the catalytic converter. The ECM calculates catalytic converter efficiency by
comparing the rear oxygen sensor signal to the front oxygen sensor signal. A normal oxygen sensor signal will constantly fluctuate above and below 500
mV, with the front oxygen sensor signal frequency of at least 5 Hz at 2500 RPM. Due to the effect of the catalytic converter, the rear oxygen sensor
signal frequency will be lower than the front oxygen sensor signal frequency. If the rear oxygen sensor signal coincides with the front oxygen sensor
signal a large percentage of the time, this indicates a loss in efficiency of the catalytic converter or a malfunction within the fuel system.
HEATED OXYGEN SENSOR (H02S)
The heated oxygen senor senses the oxygen concentration in the exhaust gas and convents it into a voltage which is sent to the ECM.
The heated oxygen sensor outputs about 800 mV when the air fuel ratio is richer than the theoretical ratio and outputs about 100 mV when the ratio is
leaner (higher oxygen concentration in exhaust gas.) The ECM 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 condition.
