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.
If the sensor output is below 0.06 V under enable conditions, ECM sets DTC P0131.
(This DTC might be caused by the malfunction of Heater circuit, so, check the heater circuit first. )
Item | Detecting Condition | Possible Cause | |
DTC Strategy |
•
Signal check, low | 1. Poor connection 2. Short to ground in signal circuit 3. S1 | |
General Enable Conditions |
•
Dew point end detected
•
Fuel feed back control active
•
Battery voltage > 11V
•
Exhaust Gas temperature = 280℃~800℃
•
No injector error
•
No upstream O2 sensor heater error | ||
Case1 | Enable Conditions |
•
S2 sensor voltage > 0.5V | |
DiagnosticTime |
•
25 sec | ||
Case2 | Enable Conditions |
•
Sensor in cold condition | |
DiagnosticTime |
•
0.1 sec | ||
Threshold Value |
•
Sensor voltage < 0.06V | ||
MIL ON Condition |
•
3 driving cycle | ||
※ S1 : upstream oxygen sensor / S2 : downstream oxygen sensor
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.
