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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 on board 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 idenify 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 on board diagnostics. Some form of a drive
cycle needs to be performed after DTCs have been erased from the PCM's
memory. 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
Freeze Frame Data --When an emissions related fault occurs, the OBD II system
not only sets a code but also records a snapshot of the vehicle operating parameter
to help in identifying the problem. This set of values is referred to as Freeze Frame
Data and may include t engine parameters such as engine RPM, vehicle speed, air
flow, engine load, fuel pressure, fuel trim value, engine coolant s, ignition timing
advance, or closed loop status.
