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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)
Once the vehicle is running, the OBDII 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
6. Secondary air
7. Heated Catalyst
8. A/C system
OBD II Monitor Readiness Status
OBDII systems must indicate whether or not the vehicl
e’s PCM’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 OBDII system. The purpose of recording readiness
status is to allow inspectors to determine if the vehicle
’s OBDII system has
tested all the components and/or systems.
The powertrain control module (PCM) sets a monitor to
“Ready” 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
