For 1990-2009 cars

### Circuit Description

The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity for 100 seconds. During the monitoring period, the PCM counts the number of times that a rich to lean and lean to rich response is indicated and adds the amount of time it took in order to complete all transitions. With this information, an average time for each transition can be determined. If the average response time is too slow, a DTC P0133 will be set.

A lean to rich transition is indicated when the HO2S voltage changes from less than 300 mV to more than 600 mV. A rich to lean transition is indicated when the HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly is likely to be inoperative and should be replaced.

### Conditions for Running the DTC

• | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201-P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.

• | The vehicle is not in Park or Neutral.

• | The engine has been running for at least 4 minutes.

• | The mass air flow is between 8 and 35 grams/second.

• | The engine speed is between 550-3000 RPM.

• | The throttle angle is between 3-35 percent.

• | The system voltage is between 9-18 volts.

• | The engine coolant temperature is more than 70°C (158°F).

### Conditions for Setting the DTC

• | The HO2S 1 lean to rich average transition response time was more than 95 milliseconds.

• | HO2S 1 rich to lean average transition response time was more than 105 milliseconds.

### 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.

• | Clear the MIL and the DTC with a scan tool.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step verifies that the malfunction is currently present during the average rich-to-lean and lean-to-rich transition times. With the ignition turned ON, the scan tool indicates the results of the last test for this diagnostic. The test conditions must be met in order for the scan tool to update the results of the test for this ignition cycle.

2. HO2S transition time, ratio, and switching DTCs set for multiple sensors indicate probable contamination. Before replacing the sensors, isolate and correct the source of the contamination in order to avoid damaging the replacement sensors.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Important: If any DTCs are set, except P1134, refer to those DTCs before proceeding with this diagnostic table. Refer to Diagnostic Trouble Code (DTC) List to diagnose the applicable DTC.

1. With the engine operating at normal temperature, operate the vehicle within the parameters listed in the Conditions for Running the DTC.
2. With the scan tool, monitor the Specific DTC Information for DTC P0133 until the test runs.

Does the scan tool indicate DTC P0133 failed last test?

Go to Step 3

Go to Intermittent Conditions

3 | Does the scan tool also indicate DTC P1134 failed last test? | Go to Step 6 | Go to Step 4
4 |

1. Visually/physically inspect for the following items:

• | Properly installed and secure HO2S bank 1 sensor 1--Refer to Heated Oxygen Sensor 1 Replacement .

• | Corrosion on terminals

• | Damaged wiring

• | Poor connections at the sensor, and at the PCM--Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

2. If a condition is found, repair as necessary. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5 | Inspect the exhaust system for leaks. If an exhaust leak is found, repair as necessary. Did you find and correct the condition? | Go to Step 7 | Go to Step 6
6 | Notice: Correct the source of the oxygen sensor contamination before replacing the sensor in order to prevent future contamination. Typical contamination sources include the following:

• | Fuel contamination

• | Use of improper RTV sealant

• | Engine oil or engine coolant consumption

Replace the bank 1 heated oxygen sensor. Refer to Heated Oxygen Sensor 1 Replacement .

Did you complete the replacement?

Go to Step 7

--

7 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 8

Go to Step 2

8 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | Go to the Diagnostic Trouble Code (DTC) List | System OK