Continuous Monitors:
Once the engine is running, the on board OBDII system is continuously monitoring key
engine sensors for engine misfire, and fuel demand. The continuous monitors are:
Other systems are tested only under specific operating conditions.
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:
Definitions
OBDII: On-Board Diagnostics Generation Two
DLC: Data Link Connector is the multi-pin connection used to interface the code reader with
the control modules of a vehicle.
MIL: Malfunction Indicator Lamp - same as “Service Engine Soon” or “Check Engine”. If the
MIL illuminates with a steady light, it indicates that a problem has been detected. If the MIL is
flashing a severe problem has been detected and further operation of the vehicle is
discouraged.
PCM: Powertrain Control Module, the on-board computer that controls engine and drive
train.
TCM: Transmission Control Module, the on-board computer that controls the transmission.
DTC: Diagnostic Trouble Codes Identify which section of the emission control system has
malfunctioned.
Enabling criteria also termed Enabling Conditions, are 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.
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