System Self-Adjustment; Autodiagnosis; Connection With Engine Immobilizer Device (Fiat Code) - Fiat 1998 Marea Service Manual

Marea-Marea
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System self-adjustment

The control unit is equipped with a self-adjustment function which has the task of recognizing the
changes which take place in the engine due to bedding in over time and the ageing of both the compo-
nents and the actual engine.
These changes are memorized in the form of modifications to the basic map and are designed to adapt the
operation of the system to the gradual alterations to the engine and components compared with when
they were new.
This adjustment function also makes it possible to compensate for the inevitable differences (due to pro-
duction tolerances) in components which are replaced. This allows optimum results in all vehicles without
special regulation and control operations.

Autodiagnosis

The ME 3.1 injection/ignition system also has an "autodiagnostic" function which memorizes any irregu-
larities with the sensors and actuators, facilitating their identification and correction. A fault is signalled by
the special failure warning light in the instrument panel.

Connection with engine immobilizer device (Fiat CODE)

To improve protection against theft attempts, the vehicle is equipped with an engine immobilizer (Fiat
CODE) which only allows the injection/ignition system to be activated by means of an electronic code.
Each time the key is turned to the OFF position, the Fiat CODE system completely deactivates the injec-
tion/ignition control unit.
When the ignition key is turned from OFF to ON, the following operations take place in the order given:
1. The injection/ignition control unit sends the Fiat CODE control unit a request for the secret code to de-
activate the immobilizer function.
2. The Fiat CODE control unit responds by only sending the secret code after having, in turn, received the
recognition code transmitted by the ignition key which contains a special transponder.
3. The recognition of the secret code allows the deactivation of the immobilizer function and the injec-
tion/ignition control unit can activate the normal system mangement programme.
A special two-way serial line allows the exchange of data between the injection/ignition control unit and
the Fiat CODE control unit.
If there is a failure in the Fiat CODE system it is still possible to start up the vehicle using the emergency
procedure.
Given the presence of the Fiat CODE system DO NOT carry out tests using another injec-
tion/ignition control unit during the fault diagnosis and/or functional tests. Under these circum-
stances, the Fiat CODE control unit would transfer the (unrecognized) code to the test control
unit which could then no longer be used on any other vehicles.
Copyright by Fiat Auto
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Engine
Fuel system
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