Users Manual Part 2

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MDMAXLITEA
• Type 2 misfires are the most severe type of misfire. When
a Type 2 misfire is sensed on the first trip, the computer
commands the MIL to light when the misfire is sensed. If
the computer determines that a Type 2 misfire is severe,
and may cause catalytic converter damage, it commands
the MIL to “flash” once per second as soon as the misfire
is sensed. When the misfire is no longer present, the MIL
reverts to steady “On” condition.
The Misfire Monitor is supported by both “spark ignition”
vehicles and “compression ignition” vehicles.
2. Fuel System Monitor
This Monitor uses a Fuel System Correction program, called
Fuel Trim, inside the on-board computer. Fuel Trim is a set
of positive and negative values that represent adding or
subtracting fuel from the engine. This program is used to
correct for a lean (too much air/not enough fuel) or rich (too
much fuel/not enough air) air-fuel mixture. The program is
designed to add or subtract fuel, as needed, up to a certain
percent. If the correction needed is too large and exceeds
the time and percent allowed by the program, a fault is
indicated by the computer.
The Fuel System Monitor is supported by both “spark
ignition” vehicles and “compression ignition” vehicles. The
Fuel System Monitor may be a “One-Trip” or “Two-Trip”
Monitor, depending on the severity of the problem.
3. Comprehensive Components Monitor (CCM)
This Monitor continuously checks all inputs and outputs from
sensors, actuators, switches and other devices that provide a
signal to the computer. The Monitor checks for shorts, opens,
out of range value, functionality and “rationality* (See Note).”
Rationality: Each input signal is compared against all other
inputs and against information in the computer’s memory
to see if it makes sense under the current operating
conditions.
Example: The signal from the throttle position sensor
indicates the vehicle is in a wide-open throttle condition,
but the vehicle is really at idle, and the idle condition is
confirmed by the signals from all other sensors. Based on
the input data, the computer determines that the signal
from the throttle position sensor is not rational (does not
make sense when compared to the other inputs). In this
case, the signal would fail the rationality test.
The CCM is supported by both “spark ignition” vehicles and
“compression ignition” vehicles. The CCM may be either
a “One-Trip” or a “Two-Trip” Monitor, depending on the
component.
5.5.2 Non-Continuous Monitors
The other twelve Monitors are “non-continuous” Monitors.
“Non-continuous” Monitors perform and complete their
testing once per trip. The “non-continuous” Monitors are: