Innova SD-Advisor SD35 - Glossary; OBD2 Terminology

GLOSSARY
OBD2 Terminology
45
GLOSSARY
OBD2 Terminology
The following terms and their denitions are related to OBD2 systems.
n Powertrain Control Module (PCM) - The PCM is the OBD2 accepted term for the vehicle’s “on-board
computer.” In addition to controlling the engine management and emissions systems, the PCM also
participates in controlling the powertrain (transmission) operation. Most PCMs also have the ability to
communicate with other computers on the vehicle (ABS, ride control, body, etc.).
n Monitor - Monitors are “diagnostic routines” programmed into the PCM. The PCM utilizes these programs
to run diagnostic tests, and to monitor operation of the vehicle’s emissions-related components or systems
to ensure they are operating correctly and within the vehicle’s manufacturer specications. Currently, up to
fteen Monitors are used in OBD2 systems. Additional Monitors will be added as the OBD2 system is further
developed.
NOTE: Not all vehicles support all fteen Monitors
n Enabling Criteria - Each Monitor is designed to test and monitor the operation of a specic part of the vehicle’s
emissions system (EGR system, oxygen sensor, catalytic converter, etc.). A specic set of “conditions” or
“driving procedures” must be met before the computer can command a Monitor to run tests on its related
system. These “conditions” are known as “Enabling Criteria.” The requirements and procedures vary for
each Monitor. Some Monitors only require the ignition key to be turned “On” for them to run and complete
their diagnostic testing. Others may require a set of complex procedures, such as, starting the vehicle
when cold, bringing it to operating temperature, and driving the vehicle under specic conditions before the
Monitor can run and complete its diagnostic testing.
n Complete / Incomplete - The terms “Complete” or “Incomplete” are used throughout this manual.
“Complete,” means the PCM has commanded a particular Monitor to perform the required diagnostic testing
on a system to ensure the system is operating correctly (within factory specications). The term “Incomplete”
means the PCM has not yet commanded a particular Monitor to perform diagnostic testing on its associated
part of the emissions system.
n Trip - A Trip for a particular Monitor requires that the vehicle is being driven in such a way that all the required
“Enabling Criteria” for the Monitor to run and complete its diagnostic testing are met. The “Trip Drive Cycle”
for a particular Monitor begins when the ignition key is turned “On.” It is successfully completed when all the
“Enabling Criteria” for the Monitor to run and complete its diagnostic testing are met by the time the ignition
key is turned “Off.” Since each of the fteen monitors is designed to run diagnostics and testing on a different
part of the engine or emissions system, the “Trip Drive Cycle” needed for each individual Monitor to run and
complete varies.
n OBD2 Drive Cycle - An OBD2 Drive Cycle is an extended set of driving procedures that takes into
consideration the various types of driving conditions encountered in real life. These conditions may include
starting the vehicle when it is cold, driving the vehicle at a steady speed (cruising), accelerating, etc. An
OBD2 Drive Cycle begins when the ignition key is turned “On” (when cold) and ends when the vehicle has
been driven in such a way as to have all the “Enabling Criteria” met for all its applicable Monitors. Only those
trips that provide the Enabling Criteria for all Monitors applicable to the vehicle to run and complete their
individual diagnostic tests qualify as an OBD2 Drive Cycle. OBD2 Drive Cycle requirements vary from one