Component Location
General Description
The heated oxygen sensors are mounted on the front side and the rear sied of Catalytic Converter (warm-up catalytic converter), which detects the oxygen concentration in the exhaust gas. The front HO2S signal is used to control air/fuel ratio (closed loop fuel control) and the rear HO2S signal is used to monitor front HO2S and catalyst for proper operation. The heated oxygen snesor (HO2S) produces a voltage that varies between 0V and 1V. When the air/fuel ratio is lean, the oxygen concentration in the exhaust gas increases and the front HO2S outputs a low voltage (approximately 0 ~ 0.1 V).When the air/fuel ratio is rich, the oxygen concentration in the exhaust gas decreases and the front HO2S output a high voltage (approximately 0.8 ~ 1 V). The ECM constantly monitors the HO2S and increases or decreases the fuel injection duration by using the HO2S signal, which is called closed-loop fuel control operation.
DTC Description
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. )
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | Signal check, low
| Poor connection
Short to ground in signal circuit
S1
|
General Enable Conditions | Dew point end detected
Target lambda = 1
Battery voltage > 10.7V
Exhaust gas temperature (model) : 600? ~ 800?
No upstream O2 sensor error or downstream O2 sensor ready
|
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
Diagnostic Circuit Diagram
Signal Waveform and Data
If you release the accelerator pedal suddenly after engine running about 4000 rpm, fuel supply will stop for short period and the O2 sensor service data in the Hi-Scan (Pro) will display values 200mV or lower. When you suddenly press on the accelerator pedal down, the voltage will reach 0.6 ~ 1.0 V. When you let the engine idle again, the voltage will fluctuate between 200 mV or lower and 0.6 ~ 1.0 V. In this case, the O2sensor can be determined as good.