P0133

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

IMPORTANT: If the voltage is measured with a 10 megohm Digital Voltmeter, the voltage may read as low as 0.32 volt (320 mV).

The Vehicle Control Module (VCM) supplies a voltage of approximately 0.45 volt (450 mV) between the HO2S High and the HO2S Low circuits. The Heated Oxygen Sensor (HO2S) varies the voltage from approximately 1.0 volt (1000 mV) during rich conditions to 0.10 volt (100 mV) during lean conditions.

The VCM monitors the HO2S activity for 100 seconds after the Closed Loop. During the monitor period, the VCM counts the number of times the HO2S switches from rich to lead and from lean to rich and adds the amount of time the sensor took to complete all the switches. With this information, the VCM determines an average time. If the average time to switch is too slow, a DTC P0133 sets.

When the HO2S temperature measures below 360°C (600°F), the sensor will not produce any voltage. The sensor will behave like an open circuit. This will result in an Open Loop operation.

The HO2S heater provides for a faster sensor warm-up which allows the sensor to become active in a shorter period of time. This allows the sensor to remain active during a long extended idle. The DTC P0133 determines if the HO2S is functioning properly by checking the response time of the sensor.

CONDITIONS FOR SETTING THE DTC

The following conditions will set the DTC:

^ No Throttle Position (TP) sensor DTCs.

^ No EVAP DTCs.

^ No Intake Air Temperature (IAT) sensor DTCs.

^ No Manifold Absolute Pressure (MAP) sensor DTCs.

^ No Engine Coolant Temperature (ECT) sensor DTCs.

^ No Mass Air Flow (MAF) sensor DTCs.

^ No intrusive test in progress.

^ No device controls are active.

^ The system voltage measures at least 9.0 volts.

^ The HO2S average transition time from lean to rich and rich to lean is greater than 125 ms.

^ The HO2S voltage remains between 300-600 mV (0.3-0.6 V).

Response Test Enable

^ Close Loop Low MAP not active.

^ No P0131, P0132, P0134 and P0135 DTCs.

^ Closed Loop.

^ The ECT is greater than 57°C (134°F).

^ The engine run time is greater than 75 seconds.

^ The MAF is between 15-55 g/s Engine speed is between 1100-3000 RPM.

^ The EVAP canister purge duty cycle is greater than or equal to 0%.

^ The above condition is present for more than 2 seconds.

ACTION TAKEN WHEN DTC SETS

The VCM turns the Malfunction Indicator Lamp (MIL) ON after the second test failure.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

IMPORTANT: Never solder or attempt to repair HO2S wires.

Check for the following conditions:

^ An improperly installed air intake duct.

^ The air intake duct for collapsed ducting, restrictions, or a missing or plugged air filter.

^ Throttle body and intake manifold vacuum leaks.

^ A damaged or blocked throttle body inlet.

^ Exhaust system for corrosion, leaks, or loose or missing hardware.

^ The HO2S is installed securely and the pigtail harness is not contacting the exhaust manifold or wires.

^ HO2S contamination.

^ The vacuum hoses for splits, kinks, and proper connections.

^ Excessive water, alcohol, or other contaminants in the fuel.

^ VCM sensor grounds that are clean, tight, and properly positioned.

TEST DESCRIPTION

The number below refers to the step number on the diagnostic table.

4. This step checks the ignition feed to the HO2S.