Launch CReader 5001 Manual page 9

CReader 5001/6001 English User's Manual
LAUNCH
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 service 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 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.
Fuel Trim (FT) -- Feedback adjustments to the base fuel schedule. Short-term fuel trim
refers to dynamic or instantaneous adjustments. Long-term fuel trim refers to much more
gradual adjustments to the fuel calibration schedule than short-term trim adjustments.
These long-term adjustments compensate for vehicle differences and gradual changes that
occur over time.
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