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2.6 OBD II Definitions
Powertrain Control Module (PCM) -- OBD II terminology for the
on-board computer that controls engine and drive train.
Malfunction Indicator Light (MIL) -- Malfunction Indicator Light
(Service Engine Soon, Check Engine) is a term used for the light on the
instrument panel. It is to alert the driver and/or the repair technician
that there is a problem with one or more of vehicle's systems and may
cause emissions to exceed federal standards. If the MIL illuminates
with a steady light, it indicates that a problem has been detected and the
vehicle should be serviced as soon as possible. Under certain
conditions, the dashboard light will blink or flash. This indicates a
severe problem and flashing is intended to discourage vehicle
operation. The vehicle onboard diagnostic system can not turn the MIL
off until the necessary repairs are completed or the condition no longer
exists.
DTC -- Diagnostic Trouble Codes (DTC) that identify which section
of the emission control system has malfunctioned.
Enabling Criteria -- Also termed Enabling Conditions. They are the
vehicle-specific events or conditions that must occur within the engine
before the various monitors will set, or run. Some monitors require
the vehicle to follow a prescribed “drive cycle” routine as part of the
enabling criteria. Drive cycles vary among vehicles and for each
monitor in any particular vehicle.
OBD II Drive Cycle -- A specific mode of vehicle operation that
provides conditions required to set all the readiness monitors
applicable to the vehicle to the “ready” condition. The purpose of
completing an OBD II drive cycle is to force the vehicle to run its
onboard diagnostics. Some form of a drive cycle needs to be performed
after DTCs have been erased from the PCM’s memory or after the
battery has been disconnected. Running through a vehicle’s complete
drive cycle will “set” the readiness monitors so that future faults can be
detected. Drive cycles vary depending on the vehicle and the monitor
that needs to be reset. For vehicle specific drive cycle, consult the
vehicle’s Owner’s Manual.
