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11
LAUNCH Professional 919E User Manual
signal voltage becomes almost the same as the upstream sensor signal. In
this case, the monitor fails the test.
The Catalyst Monitor is supported by “spark ignition” vehicles only. The
Catalyst Monitor is a “Two-Trip” Monitor. If a fault is found on the rst trip, the
computer temporarily saves the 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.
4. Heated Catalyst Monitor
Operation of the “heated” catalytic converter is similar to the catalytic
converter. The main dierence is that a heater is added to bring the catalytic
converter to its operating temperature more quickly. This helps reduce
emissions by reducing the converter’s down time when the engine is cold. The
Heated Catalyst Monitor performs the same diagnostic tests as the catalyst
Monitor, and also tests the catalytic converter’s heater for proper operation.
The Heated Catalyst Monitor is supported by “spark ignition” vehicles only.
This Monitor is also a “Two-Trip” Monitor.
5. EGR (Exhaust Gas Recirculation) System Monitor
The Exhaust Gas Recirculation (EGR) system helps reduce the formation
of Oxides of Nitrogen during combustion. Temperatures above 2500°F
cause nitrogen and oxygen to combine and form Oxides of Nitrogen in
the combustion chamber. To reduce the formation of Oxides of Nitrogen,
combustion temperatures must be kept below 2500°F. The EGR system
recirculates small amounts of exhaust gas back into the intake manifold,
where it is mixed with the incoming air/fuel mixture. This reduces combustion
temperatures by up to 500°F. The computer determines when, for how long,
and how much exhaust gas is recirculated back to the intake manifold. The
EGR Monitor performs EGR system function tests at preset times during
vehicle operation.
The EGR Monitor is supported by both “spark ignition” vehicles and
“compression ignition” vehicles. The EGR Monitor is a “Two-Trip” Monitor. If
a fault is found on the first trip, the computer temporarily saves the 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.
6. Evaporative System Monitor
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