A piston pump (10) for a hydraulic consumer of an electronically controlled vehicle brake system, carries a stepped piston (50, 50') and centers a sealing assembly (26, 26') which is retained in an axial direction Ax by a step (52, 52') on the stepped piston (50, 50'), on the one hand, and is retained by a spring cage (53, 53'), on the other hand. The stepped piston (50, 50') includes a plane support (54, 54') for plane support legs (55a,b,c; 55a,b,c') of the spring cage (53, 53') The stepped piston (50, 50') includes radially inwards, with respect to the support (54, 54'), a stepped bore (56, 56'), with the bore (56, 56') accommodating centering legs (57a,b,c; 57a,b,c') of the spring cage (53, 53'). Coaxially as well as inside the stepped bore (56, 56'), a spring-loaded valve member (59, 59') of a non-return valve is arranged. A resetting spring (38) is supported on an abutment (41) of the bushing (18, 19) on the one hand and on the spring cage (53, 53') on the other hand The bushing (18, 19) is provided with a stop (63, 63') for the stepped piston (50, 50'), so that stepped piston (50, 50'), resetting spring (38), non-return valve, and sealing assembly (26) are arranged within the bushing (18, 19) as a subassembly that can be handled independently.