5
Continuous 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:
1. Misfire 2. Fuel System 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 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
2.5 OBD II Monitor Readiness Status
OBD II systems must indicate whether or not the vehicle'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 OBD II 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 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 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.
2.6 OBD II Definitions
Powertrain Control Module (PCM) -- OBDII terminology for the on-board computer that
controls engine and drive train. Malfunction Indicator Light (MIL) -- Malfunction Indicator
Light (Service Engine Soon, Check Engine) is a term used for the light on the instrument
panel. It is to alert the driver and/or the repair technician that there is a problem with one or
more of vehicle's systems and may cause emissions to exceed federal standards. If the
MIL illuminates with a steady light, it indicates that a problem has been detected and the
vehicle should be serviced as soon as possible. Under certain conditions, the dashboard
light will blink or flash. This indicates a severe problem and flashing is intended to
discourage vehicle operation. The vehicle onboard diagnostic system can’t turn the MIL off
until necessary repairs are completed or the condition no longer exists.
