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 the 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 P1133 sets when the HO2S-1 signal has too few switches (under 300 mV to over 600 mV and vice versa) over a certain length of time.

### DTC Parameters

DTC P1133 will set if the HO2S-1 rich/lean transitions are less than 1 (auto) / 2 (manual) or lean/rich transitions are less than 1 count when:

• | The engine run time is greater than 3 minutes and 20 seconds.

• | The engine speed is between 1800-2300 RPM (auto), 2350-3000 RPM (manual).

• | The TP angle is between 8-15 percent (auto) / 22-40 percent (manual).

• | 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 P1133 diagnostic runs once per ignition cycle for a maximum of 30 seconds once the above conditions have been met.

DTC P1133 is a type B DTC.

### Diagnostic Aids

Possible causes of DTC P1133:

• | 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 P1133 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.