Fiat 1998 Marea Weekend, Руководство по обслуживанию

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Engine
Marea- Marea Weekend ©
Fuel system
99 range
10.
DIAGNOSTICS
The complete fault diagnosis of the system can be carried out through active dialogue with the diagnostic
equipment.
If a failure at the sensors is detected, the electronic control unit replaces the information coming from the
faulty sensor with pre-memorized (recovery) data to allow the operation of the engine. The detection of a
fault involves it being permanently stored in the memory and the sensor excluded from the system until
the signal is compatible again.
The same procedure is applied if the fault involves an actuator or control flap. The detection of a fault and
its replacement with recovery data means that the fault will be signalled by the special warning light in the
instrument panel coming on.
The following parameters can be managed by the control unit in the case of a breakdown: flow meter, en-
gine coolant temperature sensor, butterfly casing actuator, Lambda sensor, air temperature sensor, battery
voltage and detonation sensors. If there are problems with the control unit, the rpm sensor or the electric
fuel pump, the system does not identify the fault and the vehicle comes to a halt. The faults can be read
by the operator on the control unit using the diagnostic equipment.
Detecting faults
This is carried out during the basic function managing the sensor/actuator.
Memorizing the error and structure of the errors memory
The errors are stored in the control unit memory in the order in which they occur. For each of them the lo-
cation, type of error and ambient conditions (specific for each type of fault) measured at the time the error
was detected are memorized and there is a frequency counter.
Classification of the defect
If a defect is detected for the first time and the error state persists for a time t V 0.5s, then the defect is
memorized as "permanent". If this defect later disappears, it is memorized as "intermittent" and "not pres-
ent". If it then reappears, it remains memorized as "intermittent", but becomes "present".
The classification of a defect as "permanent" activates the recovery functions; when the fault disappears
the normal reading or implementation function is restored.
Certain types of faults are classified as "important", i.e. in terms of pollution control regulations. The pres-
ence of these faults is signalled to the user by the failure warning light in the instrument panel coming on.
Frequency counter
Each error is allocated a frequency counter which is used to determine the moment in which a fault
memorized is no longer present. The first time the fault is detected, the counter is set at 10. If the fault
disappears, the counter remains at the current value. If it reappears, it is increaed by 1 (with an upper limit
of 50).
The counter is decreased each time the engine is started up and the fault has not reappeared. If the coun-
ter reaches zero, the fault is automatically cancelled from the memory.
If after the counter has decreased, the fault reappears, the counter is returned to a value of 10 (if, on the
other hand, it was already above 10, it is not altered).
Fault signalling
The failure warning light comes on when there is a defect memorized as "present" and "important".
There is a delay of 0.1 seconds between the detection of the fault and the warning light coming on; the
delay between the fault disappearing from 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" faults already present, the warning light goes out after 4 seconds.
40 Print n° 506.763/14