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4.OBDII Readiness Monitors
An important part of a vehicle’s OBDII system is the Readiness Monitors,
which are indicators used to find out if all of the emissions components
have been evaluated by the OBDII system. They are running periodic
tests on specific systems and components to ensure that they are
performing within allowable limits.
Currently, there are eleven OBDII Readiness Monitors (or I/M Monitors)
defined by the U.S. Environmental Protection Agency (EPA). Not all
monitors are supported by all vehicles and the exact number of monitors
in any vehicle depends on the motor vehicle manufacturer’s emissions
control strategy.
Continuous Monitors
-- Some of the vehicle components or systems
are continuously tested by the vehicle’s OBDII system, while others
are tested only under specific vehicle operating conditions. The
continuously monitored components listed below are always ready:
Non-Continuous Monitors
-- Unlike the continuous monitors, many
emissions and engine system components require the vehicle to be
operated under specific conditions before the monitor is ready. These
monitors are termed non-continuous monitors and are listed below:
Comprehensive Components (CCM)
Misfire
Fuel System
EGR System
O2 Sensors
Catalyst
Evaporative System
O2 Sensor Heater
Secondary air
Heated Catalyst
A/C system
Once the vehicle is running, the OBDII system is continuously checking
the above components, monitoring key engine sensors, watching for
engine misfire, and monitoring fuel demands.
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