For 1990-2009 cars

The heated oxygen sensor 1 (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 P1134 sets when the average rich to lean and lean to rich time is smaller or greater than a certain length of time.

### DTC Parameters

DTC P1134 will set if the HO2S-1 rich/lean or lean/rich transitions are outside a calibrated range when:

• | The engine run time is greater than 60 seconds.

• | The engine speed is between 1300-3000 RPM.

• | The TP angle is between 3-35 percent.

• | The ECT is greater than 70° (158°F).

• | The fuel level is greater than 10 percent.

• | The EVAP purge solenoid DC is greater than 80 percent.

• | The loop status is closed.

• | 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 P1134 diagnostic runs once per ignition cycle for 60 seconds once the above conditions have been met

DTC P1134 is a type B DTC.

### Diagnostic Aids

Possible causes of DTC P1134:

• | An intermittent connection or corrosion in the HO2S-1 harness connector can set this DTC. Use the scan tool to monitor HO2S-1 voltage with the engine running at normal operating temperature while wiggling the signal and ground wire. Make sure the sensor is tight.

• | The most probable cause for DTC P1134 is contamination. Check for obvious contamination (oil, fuel, or engine coolant) by removing the sensor. Identify and correct the cause of the contamination if contaminated. Replace the HO2S-1.