The Lambda sensor,installed at the exhaust manifold, is planar ZrO2 dual cell type and it senses O2 density of exhaust gas for accurate EGR control through fuel correction. It also limits smoke which is generated by reach air-fuel mixture at the engine maximum loading condition. The ECM controls pumping current in order to fit λ-value from linear O2 sensor to 1.0.

Lean air-fuel mixture(1.0<λ<1.1) : The ECM supplies pumping current to Lambda sensor (+pumping current) and activates it for Lambda sensor to have the characteristic at λ=1.0 (0.0 pumping current). With the value of pumping current supplied to Lambda sensor, the ECM detects O2 density of exhaust gas.

Rich air-fuel mixture(0.9<λ<1.0) : The ECM takes away pumping current from O2 sensor (-pumping current) and deactivates it for Lambda sensor to have the characteristic at λ=1.0 (0.0 pumping current). With the value of pumping current taken away from Lambda sensor, the ECM detects O2 density of exhaust gas.This performance is the most active and fast at normal operating temp(450°C~600°C). Thus, in order to reach normal operating temp, and last at that temp, the heater(heating coil) is integrated with the Lambda sensor.

The heater coil is controlled by the ECM as PWM. The resistance of the heater coil is low when coil is cold. Thus, current through it increases while resistance is high when coil is hot thus, current decreases. With this principle, Lambda sensor temp is measured and the Lambda sensor heater operation varies based on the data.