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User Manual
Figure 2-2
2.4 OBD II Readiness 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.
Currently, there are eleven OBD II Readiness Monitors (or I/M Monitors) defined
by the U.S. Environmental Protection Agency (EPA). Not all monitors are
supported in every 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 OBD II system, while others are tested
only under specific vehicle operating conditions. The continuously monitored
components listed below are always ready:
1. Misfir
2. Fuel System
3. Comprehensive Components (CCM)
Once the vehicle is running, the OBD II system is continuously checking the
above components, monitoring key engine sensors, watching for engine misfire,
and monitoring fuel demands.
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:
1) EGR System
2) O2 Sensors
3) Catalyst
4) Evaporative System
5) O2 Sensor Heater
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