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 Readiness Monitors (or l/M Monitors)II
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 system, while others are testedII
only under specific vehicle operating conditions. The continuously
monitored components listed below are always ready:
1. Misfire
2. Fuel System
3. Comprehensive Components (CCM)
Once the vehicle is running, the OBD system is continuously checkingII
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. EG R Syst em - exha ust Gas Reci rcul at ion for reduci ng gr eenhouse gase s.
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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