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72
GLOSSARY
OBD2 Monitors
vehicle has been driven in such a way as to have all the “Enabling Criteria” met for all its applicable
Monitors. Only those trips that provide the Enabling Criteria for all Monitors applicable to the vehicle to
run and complete their individual diagnostic tests qualify as an OBD2 Drive Cycle. OBD2 Drive Cycle
requirements vary from one model of vehicle to another. Vehicle manufacturers set these procedures.
Consult your vehicle’s service manual for OBD2 Drive Cycle procedures.
NOTE: Do not confuse a “Trip” Drive Cycle with an OBD2 Drive Cycle. A “Trip” Drive
Cycle provides the “Enabling Criteria” for one specic Monitor to run and complete
its diagnostic testing. An OBD2 Drive Cycle must meet the “Enabling Criteria” for all
Monitors on a particular vehicle to run and complete their diagnostic testing.
n 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.
OBD2 MONITORS
To ensure the correct operation of the various emissions-related components and systems, a diagnostic program was
developed and installed in the vehicle’s on-board computer. The program has several procedures and diagnostic
strategies. Each procedure or diagnostic strategy is made to monitor the operation of, and run diagnostic tests on, a
specic emissions-related component or system. These tests ensure the system is running correctly and is within the
manufacturer’s specications. On OBD2 systems, these procedures and diagnostic strategies are called “Monitors.”
Currently, fteen Monitors are supported by OBD2 systems. Additional monitors may be added because of Government
regulations as the OBD2 system grows and matures. Not all vehicles support all fteen Monitors. Additionally, some
Monitors are supported by “spark ignition” vehicles only, while others are supported by “compression ignition” vehicles
only.
Monitor operation is either “Continuous” or “Non-Continuous,” depending on the specic monitor.
CONTINUOUS MONITORS
Three of these Monitors are designed to constantly monitor their associated components and/or systems for proper
operation. Continuous Monitors run constantly when the engine is running.
= Comprehensive Component Monitor
= Misre Monitor
= Fuel System Monitor
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