2.4 OBD II Readiness Monitors
Readiness Monitors 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 l/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.
Comtinuous 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:
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
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 - exhaust Gas Recirculation for reducing greenhouse gases.
2. O2 Sensors - monitor and adjust air/fuel mixture.
3. Catalyst - reduces exhaust emissions.
4. Evaporative System - monitors the integrity of the fuel tank system.
5. O2 Sensor Heater - brings O2 sensor to correct operating temperature.
6. Secondary air - reduces exhaust emissions.
7. Heated Catalyst - brings catalyst to correct operating temperature.
8. A/C system - monitors system for freon leaks.
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