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/PCM 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/PCM 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/PCM detects O2 density of exhaust gas.
Rich air-fuel mixture(0.9<λ<1.0) : ECM/PCM 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/PCM 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/PCM 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.
ECM/PCM assumes the correction resistance circuit is open and shows P2626 when upstream O2 sensor is higher than 4.8V under the fuel cut condition.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Circuit continuity check | 1. Poor connection 2. Open or short power/ground in signal circuit 3. S1 |
Enable Conditions |
•
upstream O2S temp. > 720℃
•
upstream O2S voltage < 4.81V
•
No fuel cut off | |
Threshold Value |
•
sensor voltage >4.81V | |
Diagnostic Time |
•
2 sec | |
MIL ON Condition |
•
3 driving cycle |
Waveform of sensor Current Pump at IG KEY "ON" and Engine running. It fluctuates between 2V and 3V periodically.
Waveform of sensor Vertual Ground Output at IG KEY "ON" and Engine running. 2.5V is displayed.
Waveform of sensor Current Adjust at IG KEY "ON" and Engine running. It fluctuates between 2V and 3V periodically. Waveform of sensor Nernst Voltage at IG KEY "ON" and Engine running. 2.9V is displayed.
