Fiat CODE control unit

When the key is turned to ON (+15) position, the engine management control unit sends a code request to the Fiat Code control unit. When it receives the code, it compares it with the stored Master Code.

If the code comparison is successful, the engine control unit allows start-up and normal engine operation. If the Fiat Code control unit is faulty, the engine management unit manages an emergency start procedure that can be carried out using a Fiat/Lancia tester or (for petrol versions with integral injection/ignition control unit) by means of the accelerator panel.

It is absolutely forbidden to swap engine management units between cars to check their efficiency.

During diagnosis, before replacing the engine control unit, ensure the component is really defective because when the new management unit is activated, the master code is stored and the unit then becomes totally unusable on other cars.

Fiat CODE control unit

The main function of the Fiat Code ECU is to recognise keys inserted in the ignition. Acting on a request from the engine control unit, the Fiat Code ECU sends it:

• the master code (key recognised), which enables engine start-up and normal operation;
• the diagnostic code (key not recognised), which prevents engine start-up.

The Fiat Code ECU is also responsible for:

• managing key storage or re-storage;
• arranging for the master code to be stored in the engine control unit (upon a request by the engine control unit);
• Code warning light management.

Two processes between the Fiat Code and engine management unit allow them to communicate with one another:

• after the Fiat Code ECU has stored the keys, communication begins with the engine management unit, which is still BLANK. The information exchange (code registration) between the engine management unit and Fiat Code ECU is guided only by the engine control unit. The Fiat Code ECU is only enabled to respond to engine control unit enquiries;
• verification is a standard procedure that is repeated whenever the user inserts the electronic key into the ignition and turns it to ON position (+15); the verification procedure continues even when the user turns the key to START UP position (+50).

With the key turned ON (+15), the Fiat Code ECU must recognise the electronic key and its code. Two options are possible:

• recognition of the code by the Fiat Code ECU, the engine management unit enables start-up and engine operation (the Code warning light goes off);
• if code recognition is unsuccessful, the Fiat Code control unit sends a code to the engine management unit, which prevents engine start-up (the Code warning light comes on with a steady light).