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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 by all vehicles and the exact
number of monitors in any vehicle depends on the motor vebicle
manufacturer
,
s emissions control strategy.
-- 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:
Continuous Monitors
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.
-- 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:
Non-Continuous Monitors
1) EGR System
1) Misfire
2) Fuel System
3) Comprehensive Components (CCM)
2) O2 Sensors
3) Catalyst
4) Evaporative System
5) O2 Sensor Heater
6) Secondary air
7) Heated Catalyst
8) A/C system
2.5 OBD II Monitor Readiness Status
OBD II systems must indicate whether or not the vehicle
,
sPCM
,
s
monitor system has completed testing on each component.
Components that have been tested will be reported as Ready , or
Complete , meaning they have been tested by the OBD II system.
The purpose of recording readiness status is to allow inspectors to
determine if the vehicle,s OBD II system has tested all the
components and/or systems.
The powertrain control module (PCM) sets a monitor to Reade or
Complete after an appropriate drive cycle has been performed. The
drive cycle that enables a monitor and sets readiness codes to
Ready varies for each individual monitor. Once a monitor is set as
Ready or Complete , it will remain in this state. A number of
factors, including erasing of diagnostic trouble codes (DTCs) with a
scan tool or a disconnected battery, can result in Readiness Monitors
being set to Not Ready . Since the three continuous monitors are
constantly evaluating,they will be reported as Ready all of the time.
If testing of a particular supported non-continuous monitor has not
been completed, the monitor status will be reported as Not
Complete or Not Ready .
In order for the OBD monitor system to become ready, the vehicle
should be driven under a variety of normal operating conditions.
These operating conditions may include a mix of highway driving and
stop and go, city type driving, and at least one overnight-off period.
For specific information on getting your vehicle,s OBD monitor
system ready, please consult your vehicle owner,s manual.
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