Sec. 18. It is an affirmative defense to any claim under this chapter that: (1) the nonconformity, defect, or condition does not substantially impair the use, value, or safety of the motor vehicle; or (2) the nonconformity, defect, or condition is the result of abuse, neglect, or unauthorized modification or alteration of the motor vehicle by the buyer. As added by P.L.150-1988, SEC.1.