I just got a 91 Deville. In the morning after the car has sat in the garage, when I drive down the street I can here the PMV running for about 2 seconds. This is the only time it happens. After reading in the Haynes manual it indicates this is, "The Pressure Modulator Valve (PMV) will often be heard running at slow speeds as it cycles through the ABS self-test mode." Is this correct?