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10
DN606 Automotive Diagnostic Tool User's Manual
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 specic drive cycle, consult the service manual.
Note: Do not confuse a “Trip” Drive Cycle with an OBD II Drive Cycle. A “Trip”
Drive Cycle provides the “Enabling Criteria” for one specic Monitor to run and
complete its diagnostic testing. An OBD II Drive Cycle must meet the “Enabling
Criteria” for all Monitors on a particular vehicle to run and complete their
diagnosc tesng.
Warm-up Cycle - Vehicle operation after an engine off period where engine
temperature rises at least 40°F (22°C) from its temperature before starting, and
reaches at least 160°F (70°C). The PCM uses warm-up cycles as a counter to
automatically erase a specic code and related data from its memory. When no
faults related to the original problem are detected within a specied number of
warm-up cycles, the code is erased automatically.
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.
2.6 OBD II Monitors
An important part of a vehicle’s OBD II system is the Readiness Monitors, which
are indicators used to find out if all of the emissions components have been
evaluated by the OBD II system. They are running periodic tests on specific
systems and components to ensure that they are performing within allowable
limits.
Monitor operation is either “Continuous” or “Non-Continuous,” depending on the
specic monitor.
2.6.1 Continuous Monitors
Some of the vehicle components or systems are continuously tested by the
vehicle’s OBD II system, while others are tested only under specific vehicle
operating conditions. The continuously monitored components listed below are
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