Code does not work

Questions & Answers
1

where the error am I doing?

var CenterOfMass : Transform;
function Start (){
rigidbody.centerOfMass = Vector3(COM.localPosition.x * transform.localScale.x, COM.localPosition.y * transform.localScale.y, COM.localPosition.z * transform.localScale.z);
}

Error:“Assets/carcontrol1.js(23,34): BCE0005: Unknown identifier: ‘COM’.”

2

You never declared COM.
But you did declare CenterOfMass.
So replace your indications of COM by CenterOfMass