2. Detecting and cancelling faults

2. Detecting and cancelling faults

Detecting faults

This is carried out during the basic functions through which the sensor/actuator is managed.

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.

The following is memorized for each of them:

• the error code (component and type of error),
• the error counter,
• the time elapsed since the error was detected,
• two environmental conditions (specific for each type of fault) at the time the fault was detected.

Classification of the fault

If a fault is recognized for the first time and the error state persists for a certain length of time, the fault is memorized as "permanent". If this fault later disappears, then it is memorized as "not present". The classification of a fault as "permanent" activates the recovery functions: when the fault disappears, normal operation is restored.

The presence of a "permanent" fault also involves the system failure warning light in the dashboard coming on.

Frequency counter

The counter, which goes from 0 to 127 and which is activated in the case of a fault, is decreased each time the engine is started up without the fault reappearing: when the counter reaches zero, the fault is automatically cancelled from the memory.

Failure warning light

The failure warning light comes on when there is at least on "permanent" fault in the memory.

NOTE During starting, the warning light is:

• on for 4 seconds,
• off for 0.15 seconds,
• kept on/off according to whether or not there are "permanent" errors.

Cancelling of the errors

When the frequency counter reaches zero, the fault and the parameters associated with it are cancelled. The immediate cancelling of the entire errors memory takes place in the following cases:

• through the "cancel errors memory" command sent by the F/L Tester;
• by interrupting the electrical supply for the control unit (disconnecting the battery or the control unit connectors) for at least 60 seconds.

3. Activating the actuators (active diagnosis)

The following actuators are activated with the engine switched off via a command from the F/L Tester: