Fault Diagnosis; Error Recognition And Memorization; Error Frequency Counter; Error Deletion - Fiat Bravo Service Manual

Engine
Fuel system
10.

F A U L T D I A G N O S I S

Full diagnosis of the fuel injection-ignition is possible by active dialogue w i t h the Examiner or SDC sta-
tion.
If faults in the sensors are detected, the electronic control unit replaces the data coming from the faulty
sensor w i t h pre-memorized data ( r e c o v e r y ) to allow the engine to continue operating.
Detection of the fault leads to its permanent storage in memory and the exclusion of the sensor from the
system until the signal becomes compatible again.
The same procedure is applied if the fault affects an actuator or its control port. The detection of the fault
and the replacement w i t h recovery data leads to indication of a fault by the warning light on the instru-
ment panel coming on.
The devices w h i c h , in the event of a fault, can be managed by recovery from the control unit are:
- Idle speed actuator
- Ignition coils
- Fuel vapour recirculation solenoid
- Air temperature and pressure sensor
In the event of faults in the control unit or rpm sensor, the system, even though it detects the fault, can-
not replace it w i t h recovery data and the car stops. The faults can be detected in the memory of the c o n -
trol unit using the Examiner or SDC station.

Error recognition and memorization

The error is detected via a system of validations w h i c h operates as follows.
When an error is detected, this is checked for a certain period of time to avoid possible interference on
the diagnostic line. If the fault passes this stage, it is considered to be present and is stored in RAM (fil-
tered error). It is then checked that the error remains present for a further period of time (called validation
time); if this stage is also passed, the error is finally memorized (validated error) and the fault warning
light comes on. The stage of writing the error in EEPROM takes place after the ignition is switched off.

Error frequency counter

A frequency counter is assigned t o each error in order to determine the moment when a fault which is no
longer present was memorized. On first detection of a validated error, the counter is set to a fixed set val-
ue.
The counter is decremented whenever the car is started without the fault reappearing. If the counter
reaches zero, the fault is automatically deleted from EEPROM.

Error deletion

Errors can be deleted from EEPROM in two ways:
- by means of the diagnostic equipment (Examiner or SDC station), in active diagnosis
- by resetting the error frequency counter.
NOTE Disconnecting the control unit from the system, even for long periods, does not delete data
recorded in the EEPROM.
Management of the system fault warning light
To check its operation, the control unit lights up the warning light and leaves it on for about 4 seconds
whenever the ignition is switched on. The warning light then comes on whenever there is a validated er-
ror, i.e. for as long as the fault situation remains, and it goes out when the fault disappears.
62
Bravo-Brava ft 16v
- Coolant temperature sensor
- Knock sensor
- Throttle position sensor
- Lambda probe
I
'98 range
Publication no. 506.670/14