Enabling Criteria – Also termed Enabling Conditions. They are the
vehicle-specific events of 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.
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 parameters to help in identifying the problem. This set of values
is referred to as Freeze Frame Date 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.
intended to discourage vehicle operation. The vehicle onboard diagnostic
system can not turn the MIL off until necessary repairs are completed or
the condition no longer exists.
DTC – Diagnostic Trouble Codes (DTC) these identify which section of the
emission control system has malfunctioned.
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