Faulty diagnosis

FAULTY DIAGNOSIS

The entire time the vehicle is driving, the electronic control unit carries out an autodiagnostics checking the AIR BAG system and memorizing any failures. The moment a fault is detected, as well as memorizing it, it orders the Air Bag warning light to come on.

On starting, this warning light comes on for around 4 seconds (initial test stage) and then goes out. The warning light NOT coming on or NOT going out after 4 seconds indicates a failure in the Air Bag system.

Activations of the system following an impact of a certain degree of severity are also memorized by the control unit.

Fault diagnosis with FIAT/LANCIA TESTER

The faults memorized in the control unit can be analyzed using the FIAT/LANCIA TESTER or other diagnostic equipment.

The faults memorized in the control unit can be cancelled, after the fault has been repaired, using the FIAT/LANCIA TESTER or other diagnostic equipment.

NOTE In the cas of an impact which caused the activation of the system, the control unit memory cannot be cancelled and therefore it has to be replaced.
The warning light in the instrument panel remains on constantly.

During the fault diagnosis, if it is necessary to take continuity measurements on the module lines, the modules must be disconnected from the wiring and replaced with the appropriate simulation resistances.

System fault diagnosis with blink code (only if FIAT/LANCIA TESTER is not available)

As an alternative to the FIAT/LANCIA TESTER it is possible to carry out a fault diagnosis on the system by interpreting the blink codes emitted by the "AIR BAG" failure warning light in the instrument panel. To activate the fault diagnosis it is necessary, with the key inserted, to connect terminal n°3 of the electronic control unit to earth for between 1 and 5 seconds. (The warning light signalling AIR BAG system faults is connected to the control unit for terminal n°3).

The table overleaf contains the faults which can be detected and any remedies to adopt, depending on the number of flashes emitted by the warning light.

When the fault has been repaired the test must be repeated to make sure that there are no other faults. Bear in mind that the control unit communicates faults, one at a time, in descending order, until the system repairs are complete. When the repairs have been carried out the memory must be cancelled, connecting terminal n°3 of the control unit for between 5 and 10 seconds. All the errors memorized should be cancelled, one by one, repeating the procedure each time, until the cancelling of the memory is complete.