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problem and flashing is intended to discourage vehicle operation. The
vehicle onboard diagnostic system cannot 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.
OBDII 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 OBDII
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 User Manual.
Freeze Frame Data
-- When an emissions related fault occurs, the OBDII
system not only sets a code but also records the vehicle operating
parameters to help in identifying the problem. This set of values is
referred to as Freeze Frame Data and may include important engine
parameters such as engine RPM, vehicle speed, air flow, engine load,
fuel pressure, fuel trim value, engine coolant temperature, ignition timing
advance, or closed loop status.
