Hydraulic Modulator on 1999 Volvo S70

How can you tell when your hydraulic Modulator is going bad?

Asked by for the 1999 Volvo S70
If you're talking about your ABS Modulator, then I suspect your ABS light is on and there's a code for the ABS Pump Motor? If so, this is a control unit issue. The unit can be rebuilt or replaced to address this.
If I'm off base here, provide some more info so I can better advise you.