Final answer:
The output of the Electronic Control Unit (ECU) of an ABS system is the ABS indicator dash light. The other components listed, such as the exciter ring, brake treadle valve, and speed sensor, serve as inputs, not outputs to the ECU.
Step-by-step explanation:
The output of the Electronic Control Unit (ECU) of an air brake Anti-lock Brake System (ABS) would be a) The ABS indicator dash light. The ECU processes various signals and information regarding wheel speed and braking dynamics and, if it detects a potential lock-up situation, the ECU sends signals to modulate the brake pressure to prevent the lock-up. One of the ways it communicates issues or activation to the driver is through the ABS indicator light on the dashboard.
The exciter ring, brake treadle valve, and speed sensor are inputs to the ECU. The exciter ring provides the ECU with information about the rotational speed of the wheel. The brake treadle valve registers how much pressure the driver applies to the brakes, and the speed sensor measures wheel speed. These components do not act as outputs but as inputs that inform the ECU's decision-making process.