Recording faults

Full system diagnosis can be carried out by means of active diagnosis using a Fiat/Lancia Tester

If a sensor fault is recorded, the ECU replaces the input from the faulty sensor with information from its memory (recovery) to allow the engine to continue running. When a fault is recorded, it is saved permanently and the sensor excluded from the system until the signal is again compatible.

The same procedure is applied if the fault affects an actuator or an actuator control port. When a fault is recorded and the signal replaced by a recovery input, the fault is indicated by a warning light coming on on the control panel.

The ECU is able to manage the following parameters in the case of failure: idle adjustment actuator, coolant temperature sensor, butterfly valve position sensor, air temperature sensor and knock sensor. If required by an operator, anomalies may be read off the ECU using a Fiat/Lancia Tester.

Recording faults

This is carried out while running the basic function used to manage the sensor/actuator.

Memorising error and structure of error memory

Errors are memorised in the ECU in the order in which they occur in the RAM. Location and a frequency counter are memorised for each one.

Defect classification

If a defect is recognised for the first time and the error status persists for the recognition time, the defect is memorised as "permanent". If this defect then disappears, it is memorised as "intermittent". If it reappears, it again becomes "permanent".

Classification of a fault as "permanent" activates recovery functions: when the fault disappears, normal reading or activation function is restored.

Some fault types are classified as "important", i.e. significant as far as emission control regulations are concerned. A warning light comes on on the control panel when these faults occur.

Frequency counter

A frequency counter is allocated to each error to determine the moment at which a fault no longer present was memorised. When the fault is first detected, the frequency counter memorises a value of 10. If the fault disappears it is memorised as intermittent and the counter is decreased whenever the car is started without the fault reappearing; if the counter reaches 0, the fault is deleted automatically from the memory.

If the fault reappears after the counter has been reduced, the counter is always reset to 10 (or remains unchanged if alredy greater than 10).

Fault notification

A warning light comes on when a defect is saved as "present" and "important".

The delay between recording of the fault and the warning light coming on is 2.5 secondi; the delay between the fault disappearing from the memory and the warning light going off is 0 seconds.

The warning light comes on whenever the ignition key is turned to MAR. The warning light goes off after 4 seconds unless "important" faults are present.