Heated Oxygen Sensor (HO2S)-1 and -2

Heated Oxygen Sensor (HO2S)-1 and -2
The oxygen sensor-1 is installed on the exhaust manifold (pre-catalyst) and the oxygen sensor-2 is installed on the exhaust pipe (post- catalyst). Each sensor detect the concentration of oxygen in the exhaust gases.
ECM detects the air-fuel ratio of the mixture supplied to the engine by monitoring the signal (output voltage) from sensor-1. The signal (output voltage) from sensor-2 is used to detect malfunction of the three way catalytic converter.
Each oxygen sensor heater promotes activation of the oxygen sensor.