The heated oxygen sensor (H02S-1) is an electrical source that responds to oxygen content in the exhaust manifold. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the difference in oxygen between the atmosphere and exhaust gas. The PCM sends a bias voltage (399-499 mV) on the signal line, which is pulled up through high resistance. When the HO2S-1 is cold, it produces no voltage and has extremely high internal resistance. The internal resistance of the sensor is much greater than the resistance of the bias pull-up resistor. However, when the sensor heats up, it produces voltage that overrides the bias voltage. This voltage is read by the PCM to determine a rich/lean HO2S-1 signal used to adjust injector pulse width. Under normal conditions, low sensor voltage means high oxygen content/lean air-fuel mixture and vice versa. Normal sensor readings will fluctuate between 10-1065 mV. DTC P0134 will set when the HO2S-1 signal is inactive.
DTC Parameters
DTC P0134 will set if HO2S-1 is inactive (voltage is not fluctuating outside the 399-499 mV range) when:
| • | The condition exists for longer than 2 minutes and 5 seconds. |
| • | The engine run time is greater than 30 seconds. |
| • | The ECT is greater than 75°C (167°F) for at least 20 seconds. |
| • | The TP angle is between 8-56 percent. |
| • | The calculated airflow is greater than 3 g/s for at least 30 seconds. |
| • | No CKP, ECT, EVAP, fuel injector, fuel tank pressure, fuel trim, IAT, idle speed, MAP, misfire, PCM internal fault, or TP sensor DTCs have been set. |
DTC P0134 diagnostic runs continuously once the above conditions have been met.
P0134 is a type B DTC.
Diagnostic Aids
To locate an intermittent problem, use the scan tool to monitor HO2S-1 voltage with the engine at normal operating temperature. Bias voltage (399-499 mV) will appear on the scan tool if circuit 412 or 413 is open.
Normal scan tool readings in closed loop will show HO2S-1 voltage varying between 10-1065 mV.
