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drive etc.) before the monitor is ready to be tested. These monitors are termed
non-continuous monitors and are listed below:
1. EGR System - Exhaust Gas Recirculation for reducing greenhouse gases.
2. O2 Sensors - Used to monitor and adjust air/fuel mixture.
3. Catalyst - Used to reduce exhaust emissions.
4. Evaporative System - Used to monitor the integrity of fuel tank system.
5. O2 Sensor Heater - Brings 02 sensor to correct operating temperature.
6. Secondary air - Used to reduce exhaust emissions.
7. Heated Catalyst - Brings catalyst to correct operating temperature.
8. A/C system - monitors system for freon leaks.
2.5 OBD II Monitor Readiness Status
OBD II systems must indicate whether or not the vehicle’s PCM’s monitoring has
completed testing on each emission component. Components that have been OBD
II tested will be reported as “OK”. The purpose of recording readiness status is to
allow inspectors to determine if the vehicle’s OBD II system has tested all the
emissions systems. This is handy to know before bringing vehicle to a state
emissions testing facility.
The powertrain control module (PCM) sets a monitor to “OK” after an appropriate
drive cycle has been performed. The drive cycle that enables a monitor and sets
readiness codes to “OK” varies for each individual monitor. Once a monitor is set
as “OK”, it will remain in this state. A number of factors, including erasing of
diagnostic trouble codes (DTCs) with a code reader or a disconnected battery, can
result in Readiness Monitors being set to “INC” (incomplete). Since the three
continuous monitors are constantly evaluating, they will be reported as “OK” all of
the time. As long as there are no DTCs stored in memory, the vehicle is running in
accordance with the OBD II guidelines. If testing of a particular supported non-
continuous monitor has not been completed or not tested, the monitor status will be
reported as “INC” (incomplete).
In order for the OBD monitor system to become ready, the vehicle should be driven
under a variety of 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.
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