Equus 3150 - ABS/SRS + OBD2 Diagnostic Tool - Manual (Page 29)

Onboard Diagnostics
OBD2 MONITORS
OBD2 27
Secondary Air System Monitor - When a cold engine is first
started, it runs in open-loop mode. During open-loop operation,
the engine usually runs rich. A vehicle running rich wastes fuel and
creates increased emissions, such as carbon monoxide and some
hydrocarbons. A Secondary Air System injects air into the exhaust
stream to aid catalytic converter operation:
1.
It supplies the catalytic converter with the oxygen it needs to oxidize
the carbon monoxide and hydrocarbons left over from the
combustion process during engine warm-up.
2.
The extra oxygen injected into the exhaust stream also helps the
catalytic converter reach operating temperature more quickly during
warm-up periods. The catalytic converter must heat to operating
temperature to work properly.
The Secondary Air System Monitor checks for component integrity and
system operation, and tests for faults in the system. The computer runs
this Monitor once per trip.
The Secondary Air System Monitor is a “Two-Trip” monitor. If a fault is
found on the first trip, the computer temporarily saves this fault in its
memory as a Pending Code. The computer does not command the MIL
on at this time. If the fault is sensed again on the second trip, the
computer commands the MIL “On,” and saves the code in its long-term
memory.
OBD2 Reference Table
The table below lists current OBD2 Monitors, and indicates the following
for each Monitor:
A.
Monitor Type (how often does the Monitor run; Continuous or
Once per trip)
B.
Number of trips needed, with a fault present, to set a pending DTC
C.
Number of consecutive trips needed, with a fault present, to
command the MIL “On” and store a DTC
D.
Number of trips needed, with no faults present, to erase a Pending
DTC
E. Number and type of trips or drive cycles needed, with no faults
present, to turn off the MIL
F. Number of warm-up periods needed to erase the DTC from the
computer’s memory after the MIL is turned off