Connection with the climate control system

The injectors, the fuel pump, the anti-evaporation solenoid valve and the Lambda sensor heater receive current from the fuel pump relay which is operated by the injection/ignition electronic control unit with the ignition switch in the ON position.

If there is no signal from the rpm sensor, the electronic control unit deactivates the control of the relay.

This operation is immediately reactivated as soon as, on starting up the engine, the signal arrives from the rpm sensor.

If, as a result of a fault, the fuel pump relay is not operated, the engine cannot be started up.

Connection with the climate control system

When the climate control is switched on, the compressor absorbs power from the engine which, when idling, tends to cut out. In order to avoid this problem the control unit adjusts the air flow rate to the new power requirements, operating the appropriate actuator (the adjustment also takes place in usage conditions to maintain optimum driveability). Another function of the system is to momentarily interrupt the compressor supply if the engine power requirements are high (strong acceleration).

The compressor is switched off if the temperature of the engine coolant exceeds 120 °C and is only reactivated if the temperature returns below this figure.

Connection with the engine immobilizer device

In order to improve protection against theft attempts, the vehicle is equipped with an engine immobilizer device (CODE) which only allows the injection/ignition control unit to be activated via an electronic code.

Each time the key is turned to the OFF position, the CODE system completely deactivates the injection/ignition control unit.

A special two direction serial line allows the exchange of information between the injection/ignition control unit and the CODE control unit.

If there is a failure in the CODE system it is still possible to start up the vehicle using special emergency procedures.

It is absolutely forbidden to exchange injection control units between different vehicles in order to check whether they are working or not.

During the fault diagnosis, before replacing the control unit, make sure that the component being examined is really not working properly, because when a new control unit is supplied the secret code is memorized making it impossible to use it on any other vehicles.

Fuel vapour inlet (anti-evaporation solenoid valve)

This function controls the opening of the fuel vapour inlet valve as follows:

• the solenoid valve remains closed during the starting stage, preventing the fuel vapours from excessively enriching the mixture; this condition persists until the engine coolant reaches a certain temperature.
• with the engine at operating temperature, the electronic control unit sends a square wave signal to the solenoid valve (duty-cycle operation) which modulates the opening.