P1133

Circuit Description
The powertrain control module (PCM) monitors the heated oxygen sensor (HO2S) activity for 100 seconds. During this test period the PCM counts the number of times that the HO2S signal voltage crosses the rich to lean and lean to rich thresholds. If the PCM determines that the HO2S did not switch enough times DTC P1133 is set. A lean to rich switch is determined when the HO2S voltage changes from less than 300 mV to greater than 600 mV. A rich to lean switch is determined when the HO2S voltage changes from more than 600 mV to less than 300 mV.

Conditions for Running the DTC
1. None of the following DTCs are present:
^ Throttle position (TP) sensor DTCs
^ Evaporative emissions (EVAP) system DTCs
^ Intake air temperature (IAT) sensor DTCs
^ Manifold absolute pressure (MAP) sensor DTCs
^ Exhaust gas recirculation (EGR) pintle position DTCs
^ Mass air flow (MAF) sensor DTCs
^ Engine coolant temperature (ECT) sensor DTCs
^ Crankshaft position (CKP) sensor DTCs
^ HO2S 1 heater circuit DTCs Misfire DTCs
^ Fuel trim DTCs
^ Injector circuit DTCs
2. The MAF is between 10 g/s and 30 g/s.
3. The ECT is more than 50°C (122°F).
4. The engine run time is more than 60 seconds.
5. The engine speed is between 1000 RPM and 3000 RPM.
6. The engine is running in closed loop.

Conditions for Setting the DTC
^ The above conditions are present for a 100 second monitoring period.
^ The PCM monitors fewer than 40 rich to lean and 40 lean to rich switches for HO2S 1.

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 clears after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC may be cleared by using the scan tool Clear Into function or by disconnecting the PCM battery feed.

Diagnostic Aids
A malfunction in the HO2S heater ignition feed or ground circuit may cause the DTC to set. Test the HO2S heater circuitry for intermittent malfunctions or faulty connections. If the connections and the wiring are OK and the DTC continues to set, replace the HO2S 1.
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.
4. This step checks for conditions which may cause the DTC to set with a good heated oxygen sensor. Correct any of the described conditions if present.
7. Before replacing the HO2S, check for silicon contamination.