As Afzaal Ahmad told [object object] is not a error. [object object] is a basically a array.
you can get the response
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: 'Service.svc/GetData',
data: JSON.stringify(data1),
success: function (data) {
alert(data.response);
alert(JSON.stringify(data));
},
error: function (result) {
console.log('Something went wrong', status, err);
}
});