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GLOSSARY
OBD2 Monitors
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 specific 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 specific code and related data from its memory.
When no faults related to the original problem are detected within a specified 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
specific emissions-related component or system. These tests ensure the system is running correctly and is within the
manufacturer’s specifications. On OBD2 systems, these procedures and diagnostic strategies are called “Monitors.”
Currently, fifteen 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 fifteen 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 specific 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
(CCM)
= Misfire Monitor
= Fuel System Monitor
NON-CONTINUOUS MONITORS
The other twelve Monitors are “non-continuous” Monitors. “Non-continuous” Monitors perform and complete their
testing once per trip.
= Oxygen Sensor Monitor
