OBD-II Testability Issues (MIL Illuminates During Smog Check)

When smog testing this vehicle a scan tool or smog check unit may need to be connected to the vehicle's DLC during the visual inspection MIL illumination check, depending on the testing requirements of your state.

The MIL is always illuminated when the scan tool is connected, causing a "false failure" during the "visual check" portion of the test.

Therefore, if the OBD system is used as a tachometer (RPM) source during a smog check inspection the MIL will illuminate, but it does not indicate that faults are present.

NOTE: When performing a bulb check of the MIL, the scan tool must not be connected to the DLC (OBD-II Connector).