Extinguishing Malfunction Indicator Light

When MIL is illuminated, Diagnostic Executive will turn off the MIL after 3 consecutive trips that a "Test Passed" has been reported for diagnostic test that originally caused MIL to illuminate. Although MIL has been turned off, DTC will remain stored in PCM memory (both Freeze Frame and Failure Records) until 40 warm-up cycles have occurred with no faults detected. If MIL was set by either a fuel trim or misfire-related DTC, additional requirements must be met. In addition to requirements stated in the previous paragraph, requirements are as follows:

• Diagnostic tests that are passed must occur within 375 RPM of RPM data stored at time last test failed.
• Plus or minus 10 percent of engine load that was stored at time last test failed.
• Similar engine temperature conditions (warmed up or warming up) as those stored at time last test failed.

Meeting these requirements ensures that fault which illuminated MIL has been corrected. MIL is located in the instrument panel and has following functions:

• It informs driver that a fault affecting vehicle emission levels has occurred and that the vehicle should be taken for service as soon as possible.
• As a bulb and system check, MIL will illuminate with ignition on, and engine not running. When engine is started, MIL will turn off.
• When MIL remains illuminated while engine is running, or when a malfunction is suspected due to a driveability or emissions problem, a Powertrain On-Board Diagnostic (OBD-II) System Check must be performed. Procedures for these checks are given in On-Board Diagnostic (OBD-II) System Check. See ON-BOARD DIAGNOSTIC II SYSTEM CHECK . These checks will expose faults which may not be detected if other diagnostics are performed first.

A diagnostic test is a series of steps, the result of which is a pass or fail reported to the Diagnostic Executive. When a diagnostic test reports a pass result, the Diagnostic Executive records following data:

• Diagnostic test has been completed since last ignition cycle.
• Diagnostic test has passed during current ignition cycle.
• Fault identified by diagnostic test is not currently active.

When a diagnostic test reports a fail result, the diagnostic executive records the following data:

• Diagnostic test has been completed since last ignition cycle.
• Fault identified by diagnostic test is currently active.
• Fault has been active during this ignition cycle.
• Operating conditions at time of failure.

A fuel trim DTC may be triggered by a list of vehicle faults. Make use of all information available (other DTCs stored, rich or lean condition, etc.) when diagnosing a fuel trim fault.