That light is for oil pressure and comes on when the pressure is too low.

Check the condition of the oil at the dipstick once the engine is warmed up. If there are little bubbles in the oil, you will have a serious problem and need to talk to a Volvo mechanic.

Possible problems: The oil filter is clogged and the oil is bypassing the filter.
The O rings at the bottom of the sump need to be replaced.
The "oil" is the wrong viscosity, much too light.
The oil pump is dying, very rare.
You are burning oil and it is now 2 quarts low.
Your oil is contaminated with antifreeze or gasoline, thinning it out.
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My name is Klaus and I am a V ♂ lv ♂ holic.