ABS Light: Description and Operation

WARNING: ABS and EBD are not available while Volvo Diagnostics is activated. Take great care when test driving as there is a serious risk of the wheels locking when braking.

ABS (Anti-Lock Braking System):

This is located on the instrument panel and is activated if the ABS system control module detects a fault in the ABS system. When the ignition is switched on or the engine starts, the control module switches the warning light on. The light then goes out after approx. 2 seconds if no fault is detected. If the warning light is on, the ABS system is not working but normal braking power is still available. The warning light flashes when the ABS system, DTM is activated.

When the control module DTM is disengaged, the warning light comes on for approx. 2 seconds and then goes out if no fault is detected. The warning light is controlled by a relay on the dash board. When the ABS control module grounds the signal to the relay, the relay breaks the light's ground and the light goes out. When the ABS control module increases the voltage over approx. 7 V, the relay opens and the light comes on.