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P1133

DTC P1133 O2S Insufficient Switching Sensor 1




Circuit Description
The PCM continuously monitors the oxygen sensor 1 (O2S 1) activity for 100 seconds. During the monitor period, the PCM counts the number of times that the O2S 1 switches from rich to lean and from lean to rich. You can determine a total for all of the switches with this information. If the number of switches is too low, a DTC P1133 will set.

Conditions for Running the DTC
- No active MAP DTCs
- No active IAT DTCs
- No active ECT DTCs
- No active TP DTCs
- No active fuel trim DTCs
- No active injector control DTCs
- No active misfire DTCs
- No active CKP DTCs
- No active EVAP DTCs
- No active IAC DTCs
- No active PCM memory DTCs
- ECT is more than 75° C (167° F).
- Engine speed is between 1800 RPM and 2300 RPM.
- Engine is operating in closed loop.
- Throttle position (TP) angle is between 8 percent and 15 percent.
- Evaporative emissions control system is commanded open for more than 80 percent.
- Purge learned memory is more than approximately 0.86.
- Diagnostic completes when 30 seconds accumulated time has been spent in the above conditions.

Conditions for Setting the DTC
The number of rich to lean counts is less than 1 or the lean to rich counts is less than 1.

Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool's Freeze Frame and Failure Records.

Conditions for Clearing the MIL/DTC
- The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm up cycle occurs when the coolant temperature has risen 22° C (40° F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70° C (158° F) during the same ignition cycle.
- Use the scan tool Clear Information function

Diagnostic Aids
DTC P1133 is most likely caused by one of the following:
- Fuel pressure -The system will go rich if fuel pressure is to high. The PCM can compensate for some increase, however, if it gets too high, a DTC P0172 will be set. Refer to Fuel System Diagnosis.
- Leaking injector -A leaking or malfunctioning injector can cause the system to go rich.
- MAP sensor -An output that causes the PCM to sense a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the PCM to set a fixed value for the MAP sensor. Substitute a different MAP sensor if the rich condition is gone while the sensor is disconnected.
- Pressure regulator -Check for a leaking fuel pressure regulator diaphragm by checking for the presence of liquid fuel in the vacuum line to the regulator.
- TP sensor -An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating.
- O2S 1 contamination -Inspect O2S 1 for silicone contamination from fuel or use of improper RTV sealant. The sensor may have a white powdery coating and result in a high but false voltage signal (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem.

Steps 5 - 8:




Steps 9 - 11:




Steps 12 - 15:




Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
2. This step checks for proper sensor activity. When in Closed Loop fuel control the HO2S voltage should rapidly swing above and below the bias voltage.
4. This step checks the VCM and the HIGH and LOW circuits between the VCM and the HO2S connector for proper operation.
7. This step checks for proper HO2S heater circuit operation up to the HO2S connector.
8. This step checks for proper circuit resistance between the HO2S LOW circuit and VCM ground.
13. This step checks for proper circuit resistance between the HO2S LOW circuit and VCM ground with a COLD sensor. A loose HO2S or poor tread to exhaust electrical contact will cause higher resistance when the HO2S is cold. Although 500 ohms is allowed, typical resistance should be less than 50 ohms.

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