Equus 3110 - CanOBD2 Diagnostic Tool - Manual (Page 25)

CAN OBD2 23
E
Onboard Diagnostics
OBD 2 MONITORS
After the MIL has been turned off, DTCs, Freeze Frame data,
and manufacturer-specific enhanced data stay in the com-
puter’s memory. Most of the enhanced data can only be
retrieved with special equipment such as a Scan Tool.
■ Erasing the DTCs from the computer’s memory can also turn off the
MIL. See ERASING DIAGNOSTIC TROUBLE CODES (DTCs) on
page 41, before erasing codes from the computer’s memory. If a
Code Reader or Scan Tool is used to erase the codes, Freeze
Frame data as well as other manufacturer-specific enhanced data
will also be erased.
OBD 2 MONITORS
To ensure the correct operation of the various emissions-related com-
ponents and systems, a diagnostic program was developed and
installed in the vehicle’s on-board computer. The program has several
procedures and diagnostic strategies. Each procedure or diagnostic
strategy is made to monitor the operation of, and run diagnostic tests
on, a specific emissions-related component or system. These tests
ensure the system is running correctly and is within the manufacturer’s
specifications. On OBD 2 systems, these procedures and diagnostic
strategies are called “Monitors.”
Currently, a maximum of eleven Monitors are used in OBD 2 systems.
Additional monitors may be added as a result of Government regula-
tions as the OBD 2 system grows and matures. Not all vehicles sup-
port all eleven Monitors.
Monitor operation is either “Continuous” or “Non-Continuous,”
depending on the specific monitor.
Continuous Monitors
Three of these Monitors are designed to constantly monitor their asso-
ciated components and/or systems for proper operation. Continuous
Monitors run constantly when the engine is running. The Continuous
Monitors are:
Comprehensive Component Monitor (CCM)
Misfire Monitor
Fuel System Monitor
Non-Continuous Monitors
The other eight Monitors are “non-continuous” Monitors. “Non-continu-
ous” Monitors perform and complete their testing once per trip. The
“non-continuous” Monitors are: