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 heated oxygen sensor (HO2S) system. The test may be used to set the I/M System Status to YES. The I/M System Status display on the scan tool provides an indication of whether the control module has completed the required test. The required test is complete when either all of the DTCs comprising the test have Run and Passed, or when any one of the DTCs comprising the test has illuminated the malfunction indicator lamp (MIL). Once the test is complete, the I/M System Status display will indicate YES in the Completed column.

### Conditions for Running

• | The engine coolant temperature (ECT) is less than 45°C (113°F).

• | The battery voltage is between 11.6-16 volts.

### Diagnostic Aids

The HO2S Heater Tests will normally run within the 2 minutes allotted in the procedure. If there is an indeterminate condition, the test may take up to 2 hours on some vehicles before a decision of pass or fail is made. If the test does not update to YES, it may have aborted due to the loss of enabling conditions.

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.

Step | Action | Value(s) | 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 |

Important: Whenever the ignition is turned ON, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn OFF the ignition for approximately 5 minutes to allow the sensors to cool before continuing with the test.

1. Preprogram the scan tool with the vehicle information before the ignition is turned ON.
2. Ensure the vehicle is within the Conditions for Running specified in the supporting text.
3. Set the vehicle parking brake.
4. Verify the transmission is in Park for automatic transmissions and Neutral for manual transmissions.
5. Turn OFF all of the accessories, e.g., A/C, blower fan, etc.
6. Start the engine and allow the engine to idle for the specified time or until the I/M System Status indicator updates to YES.

Did the HO2S Heater System Status update to YES?

2 minutes

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 | Go to Step 4
4 |

1. Refer to Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test.
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 the procedure until the scan tool indicates the diagnostic test has run. This may take up to 2 hours.
7. Repeat steps 4-6 for any additional required DTCs that have not run.
8. Observe the I/M System Status display with a scan tool.

Did the HO2S Heater 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 | System OK