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5
OBD II 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 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 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:
1. Misfire
2. Fuel System
3. Comprehensive Components (CCM)
DTC EXAMPLE
P0202
Systems Identifying
B = Body Sub-Systems specific
C = Chassis 1 = Fuel & Air Metering
malfunctioning
P = Powertrain 2 = Fuel & Air Metering section of the
U = Network 3 = Ignition System or systems
Engine Misfire
4 =
Auxiliary Emissions Controls
5 = Vehicle Speed Control
Code Type & Idol Controls
0 = Generic 6 = Computer Output Circuits
1 = Manufacturer 7 = Transmission Controls
Specific 8 = Transmission Controls
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