Exhaust Fumes Control; Exhaust Gas Recirculation Control; Air Conditioning System Engagement Control; Engine Immobilizer Function Control - Fiat 1998 Marea Service Manual

Marea- Marea Weekend ft ™ft -™
99 range

Exhaust fumes control

Through this function the control unit limits any exhaut fumes which could occur during fierce accelera-
tion.
To satisfy this requirement, the control unit processes the signals from the accelerator pedal potentiometer,
the rpm sensor and the intake air quantity sensor (flow meter) and operates the fuel pressure regulator and
the injectors to meter the quantity of fuel to be injected.

Exhaust gas recirculation control

According to the signals from the rpm sensors, the quantity of intake air, the temperature of the engine
coolant and the position of the accelerator pedal, the injection control unit calculates the operating times
for the EGR solenoid valve so that the exhaust gases are only partly recirculated in certain engine operat-
ing conditions.

Air conditioning system engagement control

The injection control unit manages the operation of the air conditioning system compressor electro-
magnet coupling following a logic aimed at avoiding operating conditions which would adversely affect
engine performance.
When the compressor is switched on, the injection control unit increases the quantity of fuel at the idle
speed to help the engine adjust to the greater power requirements and interrupts the supply to the com-
pressor in the following conditions:
- high power requirements by the engine (fierce acceleration);
- excessive engine coolant temperature.

Engine immobilizer function control

The system is equipped with an engine immobilizer function. This function is achieved thanks to the pres-
ence of a special control unit (Fiat CODE) capable of conversing with the injection control unit and an
electronic key with a special transmitter for sending a recognition code.
Each time the key is turned to the OFF position, the Fiat CODE system completely deactivates the injec-
tion control unit.
When the key is turned to the ON position, the following operations take place in order:
1. the injection control unit (whose memory contains a secret code) sends the Fiat CODE control unit a
request for the latter to send the secret code to deactivate the immobilizing 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;
3. the recognition of the secret code allows the deactivation of the immobilizer function on the injection
control unit and normal operation can be resumed.
Autodiagnosis
The complete electronic fault diagnosis of the injection system can be achieved by connecting the special
equipment (EXAMINER or SDC) to the diagnostic socket.
The system is also equipped with an autodiagnostic function which recognizes, memorizes and signals any
possible failure.
If a fault is detected in the sensors or actuators, the signal reconstruction strategies are immediately acti-
vated (recovery) so that the operation of the engine at an acceptable level is guaranteed without adversely
affecting the operation. \311 it is possible to drive the vehicle to a service centre for appropritate repairs.
Copyright by Fiat Auto
Engine
Fuel system
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