For 1990-2009 cars

The oxygen sensor 1 (02S-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 (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 P0133 sets when the O2S-1 signal rich to lean or lean to rich average response time is too slow.

### DTC Parameters

DTC P0133 will set if the average response time of the LEAN to RICH switches is greater than 140 ms, 125 ms (2000 Model Year), or the average response time of the RICH to LEAN switches is greater than 225 ms, 156 ms (2000 Model Year), for 100 seconds when:

• | The engine speed is between 1500-3200 RPM.

• | The loop status is closed.

• | The calculated air flow is between 7-25 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, or throttle position (TP) sensor DTCs have been set.

DTC P0133 diagnostic runs once per ignition cycle once the above conditions have been met.

DTC P0133 is a type B DTC.

### Diagnostic Aids

Possible causes of DTC P0133:

• | 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 wire. Make sure the sensor is tight.

• | The most probable cause for DTC P0133 is contamination. Check for obvious contamination (oil, fuel or engine coolant) by removing sensor. Identify and correct the cause of the contamination if contaminated. Replace the O2S-1.