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.
If there is abnormal response rate of HO2S under enable conditions, ECM sets DTC P0133.
( This DTC might be caused by the malfunction of Heater circuit, so, check the heater circuit first. )
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Response rate | ● Poor connection ● leak or clog in intake air system ● Injector ● Fuel pressure ● B1S1 ● ECM |
Enable Conditions | ● Engine speed 1800∼2800rpm ● Engine load 30∼65% ● Exhaust gas temperature (model) > 450℃ | |
Threshold Value | ● Cycle period of B1S1 signal > 3 sec | |
Diagnostic Time | ● 12 cycle | |
MIL | ● ON |
※ B1S1 : upstream oxygen sensor / B1S2 : downstream oxygen sensor
A/F Ratio | Output Voltage (V) |
Rich | 0.6 ~ 1.0 V |
Lean | 0 ~ 0.4 V |
