Troubleshooting

The electrical connections between the single components (e.g. the four wheel revolution sensors, the warning light, the brake light switch, the diagnostic socket, the power lines, etc.) form a single wiring harness equipped with a 31 pin connector. The wiring harness is protected from atmospheric agents with a sheath to prevent oxidation or corrosion with consequent false ECU input signal levels and system faults.

The ECU is directly powered by the battery via two fuses - one with a fusing current of 60A protected by a cover on the two terminals - and by the ignition switch via a 10A fuse with protected terminal.

Two relays in the ECU power the eight solenoid valves and the recovery cylinder according to the controls of the ECU.

The brake pedal switch circuit closes in the ECU when the brake pedal is pressed. This connection is used by the ECU to control braking in particular conditions. The signal is not essential. Consequently, its missed connection does not effect system operation. For this reason, the problem is not signalled by the warning light.

The red warning light is located on the instrument panel. It is powered via the ignition switch (+15V) and by the ABS ECU. The warning light comes on in the event of faults to signal that the ABS system has been deactivated and that the traditional braking system is being used.

TROUBLESHOOTING

Faults in the Bosch 5.3 ABS system components can be sought and identified by connecting one of the following tools to the diagnostic socket:

• Fiat-Lancia Tester
• S.D.C. - Computer-based diagnostic station
• Examiner

The ABS system will be disabled and the warning light will stay on while the Tester is connected.

The system will be disabled and the warning light will come on if the ECU detects a fault. This problem is stored in the permanent memory and will be deleted either by the Tester at the end of the diagnostic procedure or automatically after 20 start-ups.

The ECU will only store one error, if two errors are present at the same time.