Oxygen Sensor, General

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 air4uel ratio of the mixture supplied to the engine by monitoring the signal (output voltage) from sensor-1. The signal (out-put 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.