strex SP50 - OBD II Key Definitions

50
OBD II Denitions
Powertrain Control Module (PCM):
The OBD II terminology for the onboard computer that controls the engine and the 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 the 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
ash. This indicates a severe problem and ashing is intended to discourage vehicle operation. The
vehicle onboard diagnostic system can not turn the MIL o until necessary repairs are completed or
the condition no longer exists.
DTC:
Diagnostic Trouble Codes (DTC) identify which section of the emission control system has
malfunctioned.
Enabling Criteria:
Also termed Enabling Conditions. They are the vehicle-specic events of 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.
OBD II Drive Cycle:
A specic mode of vehicle operation that provides conditions required to set all the readiness
monitors applicable to the vehicle to the “ready” condition. The 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 DTCs 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-specic drive cycles, consult the vehicle’s Owner’s Manual.
Freeze Frame Data:
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. This set of
values and operating parameters helps in identifying the problem. This set of values is referred to
as Freeze Frame Date and may include important engine engine parameters such as engine RPM,
vehicle speed, airow, engine load, fuel pressure, fuel trim value, engine coolant temperature,
ignition timing advance, or closed loop status.