Fiat Bravo Service Manual page 394

Bravo $
2 0 v
Engine
Fuel system
10.
DIAGNOSIS
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 de­
tection 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 war­
ning 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) mea­
sured 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 me­
morized as "permanent". If this defect then disappear, it is memorized as "intermittent" and "not pre­
sent". 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 dis­
appears 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 pre­
sence 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, ho­
wever, 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 de­
lay 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 "impor­
tant" problems already present, the warning light goes out after 4 seconds.
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