Detecting problems

The complete diagnosis of the system is possible through active dialogue with the Fiat/Lancia Tester.

If a failure is detected for the sensors the electronic control unit replaces the information coming from the faulty sensor with information memorized (recovery) so that the engine can still operate. The detection of the problem involves it being memorized permanently and the exclusion of the sensor from the system until the signal is compatible once again.

The same procedure is applied if the problem involves an actuator or its control holder. The detection of the problem and the replacement with recovery data involves signalling the problem by the special warning light in the instrument panel coming on.

The parameters which can, in the case of a breakdown, be managed by the control unit are: flow meter, idle adjustment actuator, coolant temperature sensor, butterfly valve position sensor, Lambda sensor, air temperature sensor, battery voltage and detonation sensors. If there are problems with the control unit, the timing sensor or the injectors, the system does not detect the problem and the vehicle breaks down. The problems can be read by an operator on the control unit using the Fiat/Lancia Tester.

Detecting problems

This is carried out during the basic function which manages the sensor/actuator.

Memorizing the error and the structure of the errors memory

The errors are memorized in the control unit in the order in which they occur in the RAMS. For each of them the location and type of error, 2 environmental conditions (specific to each type of problem) measured the moment in which the problem is detected and a frequency counter is memorized.

Classification of the defect

If a defect is recognized for the first time and the error state persists for a time t > 0.5s, the defect is memorized as "permanent". If this defect then disappear, it is memorized as "intermittent" and "not present". If it then reappears, it remains memorized as "intermittent", but becomes "present".

The classification of a problem as "permanent" activates the recovery functions; when the problem disappears the normal function of reading or implementation is restored.

Certain types of problem are classified as "important", i.e. in terms of anti-pollution regulations. The presence of these problems is signalled to the user by means of the failure warning light in the instrument panel coming on.

Frequency counter

For each error there is a frequency counter, which is used to determine the moment in which a problem which is no longer present has been memorized. The first time the problem is detected, the counter is set at 10. If the fault disappears, the counter remains at the current value. If it reappears, it is increased by 1 (to an upper limit of 50).

The counter is decreased each time the engine is started up without the fault reappearing. If the counter reaches zero then the fault is automatically cancelled from the memory.

If after having decreased the counter the fault should reapper, the counter returns to a value of 10 (if, however, it is greater than 10, it is not altered).

Signalling failures

The failure warning light comes on when there is a defect memorized as "present" and "important". The delay time between detecting the problem and the warning light coming on is 0.1 seconds; the delay time between the disappearance of the problem in the memory and the warning light going out is 4 seconds.

The warning light comes on each time the ignition key is turned to the ON position. If there are "important" problems already present, the warning light goes out after 4 seconds.