Description
The purpose of this test is to satisfy the enable criteria necessary to execute inspection/maintenance (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 tests. The I/M System Status does not indicate that the tests have passed or failed. 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 other tests for that system have not run.
Conditions for Running
| • | The engine coolant temperature (ECT) is less than 35°C (95°F). |
| • | The intake air temperature (IAT) is less than 35°C (95°F). |
| • | The difference between the IAT and the ECT is less than 6°C (10.8°F). |
| • | The battery voltage is between 10-18 volts. |
| • | The engine speed is between 600-3,000 RPM. |
| • | The mass air flow (MAF) is between 4-26 grams per second. |
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 8 minutes on some vehicles before a decision of pass or fail is made. If the test does not update to YES, it may have failed or aborted due to the loss of enabling conditions. Extremely high ambient temperatures may prevent the HO2S Heater Test from initiating.
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 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 | |
2 |
Important: Whenever the ignition is turned ON, ignition positive voltage is supplied to the heated oxygen sensor (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. 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 - Vehicle in Vehicle DTC Information | Go to Step 4 |
4 |
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 - Vehicle in Vehicle DTC Information | System OK |
