oil light on 2002 Chevrolet Cavalier

oil light come on at idle

Do you mean the oil pressure light? If so, is the oil level OK? If the oil level is correct the next step is to attach an oil pressure gauge to the engine to determine if the engine really has low oil pressure or the pressure sending unit is faulty.
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had this same problem with different make car it ended up being main bearing was damaged not worth fixing if body is good replace with new engine