The ABS motor relay is activated by the DSC3 control unit during certain phases of the ABS, ASC or DSC control procedure.
The ABS motor relay switches the return pump on and off.
The return pump returns the brake fluid which has collected in the accumulator back into the brake circuit between the closed inlet valve and master brake cylinder (pressure reduction phase during ABS controlled braking) or conveys the brake fluid under pressure through the opened inlet valve into the relevant wheel brake cylinder (pressure build-up phase during ASC and DSC controlled braking).