Dodge ZB 2005 Service Manual page 1123

GENERAL INFORMATION
PCM memory. The criteria may range from engine
rpm, engine temperature, and/or input voltage to
the PCM. If a problem is detected with a monitored
circuit, and all of the criteria or arming conditions
are met, a trouble code will be stored in the PCM.
It is possible that a trouble code for a monitored
circuit may not be entered into the PCM memory
even though a malfunction has occurred. This may
happen because one of the trouble code criteria
(arming conditions) has not been met.
The PCM compares input signal voltages from
each input component to specifications (the estab-
lished high and low limits of the range) that are
preprogrammed for that component. If the input
voltage is not within specifications, and other trou-
ble code criteria (arming conditions) are met, a
trouble code will store in the PCM memory.
The On Board Diagnostics have evolved to the
second Generation of Diagnostics referred to as
OBDII. These OBDII Diagnostics control the func-
tions necessary to meet the requirements of Cali-
fornia OBDII and Federal OBD regulations. These
requirements specify the inclusion of a Malfunction
Indicator Light (MIL) located on the instrument
panel for all 1994 and subsequent model-year pas-
senger cars, light duty trucks, and medium-duty
vehicles. The purpose of the MIL is to inform the
vehicle operator in the event of the malfunction of
any emission system or component failures that can
affect emissions and which provide input to, or
receive output from, the PCM.
The following table summarizes the various
OBDII monitors operation.
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