Do you have the deluxe instrument panel (lights + gauges)? Picture shows my 2003T. The oil pressure sensor is in the upper right hand corner of the picture, attached to the oil pressure pickoff near the oil filter by a tube. There are two wires coming out of it to the gauge and alarm. The alarm should come on when you turn the key, and stay on until the engine starts and the oil pressure is above the minimum (~10psi). Then go on again when the oil pressure drops below the minimum, or any of the other sensors generates an alarm. I believe the other alarms are gated by the oil pressure switch, but the gauges do show as active as soon as the key is on. You can find the wiring diagrams in the owners manual at http://members.dslextreme.com/users/j40ed/volvo_penta_2002_owner.pdf .