P0133

DTC P0133 Oxygen Sensor 1 (O2S1) Slow Response

Circuit Diagram:

Circuit Description
The Engine Control Module (ECM) continuously monitors the Oxygen sensor 1 (O2S1) activity for 100 seconds. During the monitor period, the ECM counts the number of times that the O2S1 switches from rich to lean and from lean to rich and adds the amount of time it took to complete all switches. With this information, an average time for all switches can be determined. If the average time to switch is too out of specification, a DTC P0133 will set.

If the O2S1 pigtail wiring, connector, or terminal is damaged, the entire O2S1 assembly must be replaced. Do not attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the O2S1 wire(s). Any attempt to repair the wires, connector, or terminals could result in the obstruction of the air reference and degrade O2S1 performance.

Conditions for Setting the DTC
- O2S1 average transition time between 0.3 - 0.6 volts is greater than;
- Lean to rich:
95 milliseconds (AT)
125 milliseconds (MT)

- Rich to lean:
140 milliseconds (AT)
156 milliseconds (MT)

- Closed loop stoichiometry.
- Engine Coolant Temperature (ECT) is greater than 70 °C (158 °F).
- System voltage is greater than 10 volts.
- Engine run time is greater than 60 seconds.
- Purge Duty Cycle (DC) is less than 20%.
- The rpm is between 1600 and 4300.
- Airflow is between 9 and 40 g/sec.
- DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0134, P1167, P0171, P1171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0337, P0351, P0352, P0401, P0402, P0404, P0405, P0406, P0502, P0506, P0507, P1404, P1441, and P0443 are not set.
- 2 second delay after conditions are met.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn off after four consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- The DTC(s) can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for more than 10 seconds.

Diagnostic Aids
DTC P0133 or slow response is most likely caused by one of the following items:
- Fuel pressure - The system will go rich if fuel pressure is too high. The ECM can compensate for some increase, but if it gets too high, a DTC P0133 may set. Refer to Fuel System Diagnosis. Testing and Inspection
- Leaking injector - leaking or malfunctioning injector can cause the system to go rich.
- Manifold Absolute Pressure (MAP) sensor - An output that causes the 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 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.
- 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.
- O2S1 contamination - Inspect O2S1 for silicone contamination from fuel or use of improper room temperature vulcanizing (RTV) sealant. The sensor may have a white powdery coating, resulting in a high but false voltage signal (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) 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.
14. The replacement ECM must be reprogrammed. Refer to the latest Techline procedure for ECM reprogramming.
17. If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.

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