P0133

Circuit Description
The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity for 100 seconds. During the monitoring period the PCM counts the number of times that the a rich to lean and lean to rich response is indicated and adds the amount of time it took to complete all transitions. With this information, an average time for each transition may be determined. If the average response time is too slow, a DTC P0133 is set. A lean to rich transition is indicated when the HO2S voltage changes from less than 300 mV to more than 600 mV. A rich to lean transition is indicated when the HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly is likely to be malfunctioning and should be replaced.

Conditions for Running the DTC
None of the following DTCs are present:
- Throttle position (TP) sensor DTCs
- Evaporative emissions (EVAP) DTCs
- Intake air temperature (IAT) sensor DTCs
- Manifold absolute pressure (MAP) sensor DTCs
- Exhaust gas recirculation (EGR) pintle position DTCs
- Engine coolant temperature (ECT) sensor DTCs
- Crankshaft position (CKP) sensor DTCs
- Mass air flow (MAF) sensor DTCs
- Misfire DTCs
- Fuel trim DTCs
- Fuel injector circuit DTCs
^ The engine is running in closed loop fuel control for at least 60 seconds.
^ The engine speed is between 1000 RPM and 3000 RPM.
^ The ECT is more than 50°C (122°F).
^ The MAF is between 10 g/s and 30 g/s.

Conditions for Setting the DTC
HO2S 1 lean to rich average transition response time during the sample period was longer than 145 milliseconds or rich to lean average transition response time during the sample period was longer than 135 milliseconds.

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has run and failed.
^ The PCM stores the conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL off during the third consecutive trip in which the diagnostic has run and passed.
^ The history DTC clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids
Inspect for the following conditions:
^ A faulty connection at the PCM. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections.
^ Inspect the wiring harness for damage. If the harness appears to be OK, observe the HO2S 1 display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the display indicates the location of the malfunction. If DTC P0133 cannot be duplicated, reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how Often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
2. Verifies that the malfunction is currently present.
3. HO2S transition time, ratio, and switching DTCs set for multiple sensors indicate probable contamination. Before replacing the sensors, isolate and correct the source of the contamination to avoid damaging the replacement sensors.