For 1990-2009 cars

The oxygen sensor 1 (O2S-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 powertrain control module (PCM) sends a bias voltage, 391-491 mV on the signal line which is pulled up through high resistance. When the O2S-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 O2S-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 10-999 mV. DTC P1133 sets when the O2S-1 signal has too few switches over a certain length of time.

### DTC Parameters

DTC P1133 will set if the O2S-1 signal has not switched greater than 10 times within a 100 second test when:

• | The engine speed is between 1,500-3,000 RPM.

• | The Loop status is closed.

• | The calculated air flow is greater than 7 gm/s.

• | No camshaft (CAM), crankshaft position (CKP), engine coolant temperature (ECT), exhaust gas recirculation (EGR), evaporative emission (EVAP) purge solenoid, fuel trim, intake air temperature (IAT), manifold absolute pressure (MAP), misfire, O2S-1, system voltage or throttle position (TP) sensor DTCs have been set.

DTC P1133 diagnostic runs once per ignition cycle 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 O2S-1 harness connector can set this DTC. Use a scan tool to monitor O2S-1 voltage with engine running at normal operating temperature while wiggling the signal and ground (circuit 413) 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 O2S-1.