Extinguishing the MIL

When the MIL is ON, the diagnostic executive will turn OFF the MIL after 3 consecutive trips that a test passed has been reported for the diagnostic test that originally caused the MIL to illuminate. Although the MIL has been turned OFF, the DTC will remain in the ECM memory, both Freeze Frame and Failure Records, until 40 warm-up cycles after no faults have been completed.

If the MIL was set by either a fuel trim or misfire-related DTC, additional requirements must be met. In addition to the requirements stated in the previous paragraph, these requirements are as follows:

• The diagnostic tests that are passed must occur with 375 RPM of the RPM data stored at the time the last test failed.
• Plus or minus 10 percent of the engine load that was stored at the time the last test failed. Similar engine temperature conditions, warmed up or warming up, as those stored at the time the last test failed.

Meeting these requirements ensures that the fault which turned ON the MIL has been corrected.

The MIL is on the instrument panel and has the following functions:

• It informs the driver that a fault that affects vehicle emission levels has occurred and that the vehicle should be taken for service as soon as possible.
• As a system check, the MIL will come ON with the key ON and the engine not running. When the engine is started, the MIL will turn OFF.
• When the MIL remains ON while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, an EOBD System Check must be performed. The procedures for these checks are given in EOBD System Check. These checks will expose faults which may not be detected if other diagnostics are performed first.