Heated Oxygen Sensor-1 and -2

HEATED OXYGEN SENSOR-1 (HO2S-1)
The oxygen sensor is installed on the exhaust manifold (pre-catalyst) to detect the concentration of oxygen in the exhaust gases.

The oxygen sensor heater promotes activation of the oxygen sensor.




HEATED OXYGEN SENSOR-2 (HO2S-2)
The oxygen sensor is installed on the exhaust pipe (post-catalyst) to detect the concentration of oxygen in the exhaust gases just like HO2S-1.

ECM (PCM) judges deterioration of TWC (three way catalytic converter) by comparing waveforms of the output voltage from HO2S-1 and HO2S-2.