he powertrain control module (PCM) sets a monitor to „Ready“ or „Complete“after an
appropriate drive cycle has been performed. he drive cycle that enables a monitor and
sets readiness codes to „Ready“ varies or 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 (D Cs) with a code reader or a disconnected battery,
can result in Readiness Monitors being set to „Not Ready“. Since the tree 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 a variety of normal operating conditions. hese 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 O B II efinitions
Powertrain Control Module (PCM) – – OBD II 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. his indicates a severe problem and flashing is intended to
discourage vehicle operation. he vehicle onboard diagnostic system can not turn the
MIL off until the necessary repairs are completed or the condition no longer exists.
TC – – Diagnostic rouble Codes that identify which section of the emission control
system has malfunctioned.
Enabling Criteria – – Also termed Enabling Conditions. hey are the vehicle-specific
events or conditions that must occur within the engine before the various monitors will
set, or run. Some monitors require the vehicle to follow a prescribed „drive cycle“
routine as part of the enabling criteria. Drive cycles vary among vehicles and for each
monitor in any particular vehicle.
OB II rive Cycle – – A specific mode of vehicle operation that provides conditions
required to set all the readiness monitors applicable to the vehicle to the „Ready“
condition. he purpose of completing an OBD II drive cycle is to force the vehicle to run
its onboard diagnostics. Some form of a drive cycle needs to be performed after D Cs
have been erased from the PCM's memory or after the battery has been disconnected.
Running through a vehicle's complete drive cycle will „set“ the readiness monitors so
that future faults can be detected. Drive cycles vary depending on the vehicle and the
monitor that needs to be reset. For vehicle specific drive cycle, consult the vehicle's
Owner's Manual.
Freeze Frama ata – – When an emissions related fault occurs, the OBD II system
not only sets a code but also records a snapshot of the vehicle operating parameters to
help in identifying the problem. his set of values is referred to as Freeze Frame Data
and may include important engine parameters such as engine RPM, vehicle speed, air
flow, engine load, fuel pressure, fuel trim value, engine coolant temperature, ignition
timing advance, or closed loop status.
4
