P1133

CIRCUIT DESCRIPTION
The Powertrain Control Module (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 Diagnostic Trouble Code (DTC) P1133 will set.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201-P0204, P0300, P0301-P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
^ The Engine Coolant Temperature (ECT) is more than 70°C (158°F).
^ The engine speed is between 1,600-2,450 RPM.
^ The fuel level is greater than 10 percent.
^ The engine is operating in Closed Loop.
^ The Throttle Position (TP) angle is between 9-16 percent.
^ The Evaporative Emissions (EVAP) control system is commanded open for more than 36 percent.
^ The purge learned memory is more than approximately 0.78.
^ The 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 2 or the lean to rich counts is less than 2.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
DTC P1133 is most likely caused by one of the following:
^ Fuel pressure-The system will go rich if fuel pressure is too high. The PCM can compensate for some increase, however, if pressure gets too high a DTC P0172 will be set. Refer to Fuel System Diagnosis. Component Tests and General Diagnostics
^ 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 Manifold Absolute Pressure (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.
^ The Throttle Position (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.

TEST DESCRIPTION

Steps 1-8:

Steps 9-15:

The numbers below refer to the step numbers on the diagnostic table.
2. This step tests 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 tests the PCM and the HIGH and LOW signal circuits between the PCM and the HO2S connector for proper operation.
7. This step tests for proper HO2S heater circuit operation up to the HO2S connector.
8. This step tests for proper circuit resistance between the HO2S LOW signal circuit and PCM ground.
11. Probable causes include the following: poor O2S LOW terminal contact at PCM, poor PCM ground connection, high PCM ground circuit resistance and an ungrounded exhaust system.