P0133

Diagnostic Chart:

Wiring Diagram:

Circuit Description
The VCM supplies a voltage of approximately 0.45 volt (450 mV) between the HO2S High and the HO2S Low circuits. If a 10 megohm digital voltmeter measures this voltage, the voltage may read as low as 0.32 volt. The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1.0 volt (1000 mV) if the exhaust is rich to as low as 0.1 volt (100 mV) if the exhaust is lean.

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 Diagnostic Trouble Code (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. This DTC is a type B DTC.

Conditions for Setting the DTC
The following conditions will set the DTC:

^ No TP sensor DTCs.
^ No EVAP DTCs.
^ No IAT sensor DTCs.
^ No MAP sensor DTCs.
^ No ECT sensor DTCs.
^ No MAF sensor DTCs.
^ Misfire DTCs not active.
^ No intrusive test in progress.
^ No device controls are active.
^ The system voltage measures at least 9.0 volts.

Response Test Enable

^ A Closed Loop low MAP not active.
^ A Closed Loop Mode 0 not active.
^ The DTCs P0131, P0132, P0134 and P0135 are not present.
^ Closed Loop.
^ The ECT is greater than 57°C.
^ The engine run time is greater than 75 seconds.
^ The MAF is at least 15 grams per second but less than 55 grams per second.
^ Engine speed is at least 1100 RPM but less than 3000 RPM.
^ The EVAP canister purge duty cycle is greater than 0%.
^ The above condition is present for more than 2 seconds.

Action Taken When DTC Sets
The VCM turns on the Malfunction Indicator Lamp (MIL) after the second test failure.

Conditions for Clearing the MIL/DTC
The VCM turns the MIL off after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen
40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.

Diagnostic Aids
Check the HO2S heater operation.

NOTE: Never solder the HO2S wires. For proper wire and connector repairs refer to Wiring Repairs in Engine Electrical.

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

4. This step checks for physical damage to the engine components and the converter.