Fiat Bravo Service Manual page 172

77poCig|i6v Engine
Fuel system
10.
b. Microprocessor
This electronic component is responsible for computing and managing acquired data. It is thus a true
computer and its main tasks include: consulting memories, comparing data input with sample data,
managing actuator control circuits.
c. ROM memory (Read Only Memory-memoria di sola lettura)
This contains all programs necessary for microprocessor operation. Because the unit is programmed
permanently prior to installation, data may be read but not modified.
The ROM memory is conservative; commands are saved even when the battery leads are disconnect­
ed.
d. RAM memory (Random Access Memory)
The RAM memory is a transitional memory where data can be read and saved.
This memory is actually used to save input data temporarily so that they are available for processing
and also to memorize signals for coding operating anomalies that may occur within sensors, actuators
or ECU functions.
The RAM memory is divided into sections: the first volatile part, for data memorization, is enabled
with ignition key in MARCIA position and deleted in STOP position.
The second non-volatile part, (RAM STAND-BY) saves engine parameters and adapts them in time. In
other words, the ECU uses the Lambda probe signal to modify and store an injection time correction
factor that influences mixture concentration; this ECU is therefore defined SELF-ADAPTIVE.
These values require a continual supply from the battery in order to be maintained (memory in
STAND-BY). If the battery, dual relay or terminals are disconnected, the parameters are zeroed. Nor­
mal vehicle use resets the adaptation process and new parameters are memorized.
The presence of a non volatile memory allows data relating to system anomalies to be saved even if
the battery is disconnected and anomalies to be indicated even once they have been absent for 5 con­
secutive start-ups (one start-up +20' engine operation).
e. EEPROM memory (Electrical Erasable Programmable Read Only Memory)
This is a special type of memory that can be deleted electrically and reprogrammed again and again.
One of its functions is to receive from the RAM STAND-BY recordings of anomalies that have arisen
during engine operation and send these through the diagnostic socket to a Fiat-Lancia Tester. A Fi­
at-Lancia Tester must be used in active diagnosis in order to delete the anomalies.
f. Drivers (final power stages for actuator control)
These circuits are driven directly by the microprocessor and the relevant integrated circuit. They are
used to supply actuators such as: injectors, step motor for idle control, carbon filter flushing valve,
fuel pump relay, ignition coil main relay.
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