For 1990-2009 cars

### Description

The purpose of this procedure is to satisfy the enable criteria necessary to execute inspection/maintenance (I/M) readiness diagnostics for the Heated Oxygen Sensor/Oxygen Sensor (HO2S/O2S) System. This procedure may be used to set the HO2S/O2S I/M System Status display on the scan tool to YES. The HO2S/O2S I/M System Status display indicates whether or not the control module has completed the readiness diagnostics. The readiness diagnostics complete when all DTCs comprising the diagnostics run and pass, or any DTC comprising the diagnostics illuminates the malfunction indicator lamp (MIL). Once the diagnostics complete, the HO2S/O2S I/m System Status display will be updated to YES.

### Conditions for Running

• | The fuel level is more than 10 percent.

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

• | The engine is running in closed loop fuel control.

• | The battery voltage is between 11-18 volts.

### Diagnostic Aids

If there is an impending failure, the system may require more time to run the diagnostics than was allotted in the system set procedure. If any DTCs do not run and no DTC is set, review the appropriate scan tool data list and service information. This will give an indication of why the DTCs do not run. Some diagnostics may abort due to changes in the conditions while the diagnostics are running. For example, changes in engine load such as a cooling fan or A/C compressor clutch turning ON, may cause the diagnostics to abort. If the HO2S/O2S I/M System Status does not update to YES, the procedure can be repeated until a YES status is achieved.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | Go to Inspection/Maintenance (I/M) System Check
2 |

1. Ensure the vehicle is within the Conditions for Running specified in the supporting text.
2. Turn OFF all of the accessories, e.g., A/C, blower fan, etc.
3. Start and allow the engine to idle for 2 minutes.

Caution: Refer to Road Test Caution in the Preface section.

Important: If the heated oxygen sensor/oxygen sensor (HO2S/O2S) inspection/maintenance (I/M) System Status updates to YES at any time during the drive procedure, disregard the remaining numbers in this step.

4. Acceleration at part throttle to 72-89 km/h (45-55 mph) with this speed maintained for 6 minutes.
5. Decelerate to 0 km/h (0 mph).
6. Accelerate at part throttle to 89 km/h (55 mph) with this speed maintained for 8 minutes.
7. Decelerate to 0 km/h (0 mph)
8. Allow the engine to idle for 2 minutes while the following criteria is maintained:

• | Service brake is depressed

• | Automatic transmission in DRIVE

• | Manual transmission in NEUTRAL with the clutch pedal depressed

9. Review the I/M System Status display with a scan tool.

Did the HO2S/O2S System Status update to YES?

Go to Step 5

Go to Step 3

3 | Observe the DTC Information with a scan tool. Does the scan tool indicate any failed DTCs? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 4
4 |

1. Refer to the Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to update the HO2S/O2S I/M System Status to YES.
2. Observe the Not Ran Since Code Cleared display with a scan tool.
3. Determine which of the DTCs required for a YES status has not run.
4. Enter the DTC number in the Specific DTC menu of the scan tool.
5. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC.
6. Repeat numbers 4-6 of this step for any additional required DTCs that have not run.
7. Observe the I/M System Status display with a scan tool.

Did the HO2S/O2S System Status update to YES?

Go to Step 5

Go to Diagnostic Aids

5 | Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK