Lambda sensor installed at 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 engine maximum loading condition. 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) : 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, ECM detects O2 density of exhaust gas.
Rich air-fuel mixture(0.9<λ<1.0) : 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, ECM detects O2 density of exhaust gas.
This performance is the most active and fast at normal operating temp.(450℃~600℃) thus, in order to reach normal operating temp. and last at that temp., heater(heating coil) is integrated with Lambda sensor.
Heater coil is controlled by ECM as PWM. the resistance of 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 Lambda sensor heater operation varies based on the data.
When ECM detects open in the heater control circuit(S1), ECM sets DTC P0030.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Heater check open | 1. Poor connection 2. Open or Short to ground in power circuit 3. Open in control circuit 4. S1 |
Enable Conditions |
•
IG ON | |
Threshold Value |
•
Open | |
Diagnostic Time |
•
Continuous | |
MIL ON Condition |
•
3 driving cycle |
※ S1 : upstream oxygen sensor / S2 : downstream oxygen sensor
Item | Specification |
Heater Resistance(Ω) | Approx. 3.2Ω ± 0.8Ω at 20℃ (68℉) |
The HO2S requires a minimum temperature to provide a closed loop fuel control system. So the HO2S contains a heater element to reduce its warm-up time and ensure its performance during all driving conditions. The HO2S heater is controlled ON after engine start except for Cold condition and high speed accelleration. The ECM controls this heater element by duty cycle. The main relay supplies voltage to the heater and the ECM provides a ground circuit for activating the heater.
