P1133

Circuit Description

The 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 will be 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

^ No active MAF, TP, IAT, MAP, ECT, EGR sensor, injector circuit, EVAP, fuel trim, or HO2S heater DTCs.
^ Above conditions present for a 100 second monitoring period after closed loop.
^ Mass Air Flow is between 10 and 30 g/s.
^ ECT is greater than 50°C (122°F).
^ Engine speed is between 1000 and 3000 RPM.

Conditions for Setting the DTC

^ The PCM monitors fewer than 40 rich to lean and 40 lean to rich switches for HO2S 1.
^ The condition is present for a 100 second monitoring period.

Action Taken When the DTC Sets

^ The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic has been run and failed.
^ If equipped with traction control, the PCM will command the Electronic Brake and Traction Control Module (EBTCM) via the serial data circuit to turn OFF traction control, and the EBTCM will illuminate the TRACTION OFF lamp.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

Diagnostic Aids

Inspect for the following:

Important: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

^ Poor terminal connection.
Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Diagrams.
^ Damaged harness.
Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault.
^ Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

4. This step Tests for conditions which may cause the heated oxygen sensor to appear faulty. Correct any of the described conditions if present.
7. Before replacing the HO2S, Test for silicon contamination.