For 1990-2009 cars

### Description

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the oxygen sensor (O2S, HO2S) system. The test may be used to set the I/M System Status to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing this test. Failure to meet the necessary requirements may produce inaccurate test results.

### Conditions for Running

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

• | The engine is running in Closed Loop fuel control.

• | The battery voltage is between 10.5-16 volts.

### Diagnostic Aids

If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the malfunction indicator lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs).

The first failure of a type B DTC does not constitute a final determination of pass or fail, and will not update the I/M System Status to YES. A second trip is required, and all the conditions to run must be met in order for the test to run again. These conditions may include a partial to complete engine cool down.

The I/M System Status will update only when an emission related DTC fails the second time, or when all of the tests pass.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.

If a diagnostic test is difficult to run, maintain necessary enable conditions until the system status updates to YES.

### Test Description

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

1. Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.

2. The oxygen sensor tests begin during the idle period immediately following the cruise period.

3. This step is to identify a first failure of a type B DTC. A DTC only appears on the I/M System Status display when the DTC becomes a MIL illuminating DTC. This occurs on the second failure of a type B DTC. A first failure of a type B DTC will not allow the I/M System Status to update to YES. Refer to Diagnostic Aids.

4. This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC.

5. The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any Emission Related DTC sets after the tests are complete, the DTC will require diagnosis.

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 idle the engine.

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.

Important: In order for this test to run, the vehicle must operate in the following conditions:

4. Accelerate the engine to 48-80 km/h (30-50 mph) and cruise for 3 minutes after the engine reaches operating temperature.
5. Deceleration to 0 km/h (0 mph).
6. Idle the engine 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

7. Accelerate at part throttle to 48-80 km/h (30-50 mph) with this speed maintained for 30 seconds.
8. With a scan tool, review the I/M System Status display.

Did the HO2S/O2S System Status update to YES?

Go to Step 5

Go to Step 3

3 | With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? | Go to Diagnostic Trouble Code (DTC) List | 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 complete this test.
2. Operate the vehicle within the Conditions for Running the DTC, located in the supporting text for the diagnostic table of the DTC.
3. Repeat the procedure until the scan tool indicates the diagnostic test has run.
4. With a scan tool, observe the I/M System Status display.

Did the HO2S/O2S System Status update to YES?

Go to Step 5

Go to Diagnostic Aids

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