P1133

Circuit Description
The powertrain control module (PCM)/engine control module (ECM) constantly monitors the oxygen sensor (O2S) activity for 100 seconds. During the monitor period, the PCM/ECM counts the number of times that the O2S switches from rich to lean and from lean to rich. With this information, a total for all switches can be determined. If the number of switches is too low, DTC P1133 will set. The lean-to-rich and the rich-to-lean are greater than 20 switches.

Conditions for Setting the DTC
- DTCs P0106, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0134, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0337, P0351, P0352, P0402, P0404, P0405, P0406, P0506, P0507, P1404, P1441 and P1627 not set.
- Engine is operating in closed loop.
- Engine Coolant Temperature (ECT) is above 147 °F (64 °C).
- The engine has been operating for at least one minute.
- Canister purge duty cycle is greater than 2%.
- Engine speed is between 1500 rpm and 3500 rpm.
- Airflow is between 9 and 28 g/sec.

Action Taken When the DTC Sets
- The PCM/ECM will illuminate the malfunction indicator lamp (MIL).
- Open loop fuel control will be in effect.
- The PCM/ECM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The PCM/ECM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P1133 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- DTC P1133 can be cleared by using the scan tool

Diagnostic Aids
DTC P1133 is most likely caused by one of the following items:
- Fuel Pressure - The system will go rich if the fuel pressure is too high. The PCM/ECM can compensate for some increase. However, if it gets too high, a DTC P1133 may set. Refer to "Fuel System Diagnosis".
- Leaking injector - A leaking or malfunctioning injector can cause the system to go rich.
- Manifold Absolute Pressure (MAP) sensor - An output that causes the PCM/ECM 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/ECM 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 pressure regulator.
- Throttle Position (TP) sensor - An intermittent TP sensor output can cause the system to go rich due to a false indication of the engine accelerating.
- O2S contamination - Inspect O2S for silicone contamination from fuel or improper use of RTV sealant. The sensor may have a white powdery coating and result in a high but false voltage signal (rich exhaust indication). The PCM/ECM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem.

Steps 1 - 5:

Steps 6 - 12:

Steps 13 - 16:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart.
1. The OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
16. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.
18. If no malfunctions have been found at this point and no additional DTCs are set, refer to "Diagnostic Aids" for additional checks and information.