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 the signal output satisfies the threshold value under enable conditions, ECM sets DTC P0134.
( 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, wiring interruption | ● Poor connection ● Open or short in signal circuit ● B1S1 ● ECM |
General Enable Conditions | ● Dew point end detected ● Required lambda = 1 ● Battery voltage > 10.7V ● Exhaust gas temperature (model) < 800℃ ● Heater control enabled | |
Case1 | Enable Conditions | ● Time after fuel cut-off > 3.0s ● B1S2 sensor voltage > 0.2V |
Threshold Value | ● 0.1 sec | |
Diagnostic Time | ● Sensor voltage > 0.2V | |
Case2 | Enable Conditions | ● Sensor voltage : 0.4~0.6V |
Diagnostic Time | ● 6 sec | |
Case3 | Enable Conditions | ● Exhaust gas temperature (model) > 600℃ |
Threshold Value | ● Internal resistance > 20 ㏀ | |
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 |
