The advent of Enhanced Inspection/Maintenance (I/M) Programs brought a need for specialized diagnostics and repair procedures to enable the proper repair of failing vehicles. Unlike previous emission testing programs. Centralized Enhanced I/M Programs such as IM240 present a unique challenge for technicians - the inability to confirm the effectiveness of the repair without the use of similar equipment. This inability to confirm that proper repairs have been made to meet IM240 requirements coupled with a desire not to risk repeat vehicle failures inspired General Motors to investigate all known equipment and procedures relative to this subject GM has conducted a study to measure the effectiveness of various IM240 repair confirmation products and procedures in predicting IM240 outcomes. Appropriate statistical methods were employed to interpret the data acquired in this study. Also collected was vehicle repair and exhaust gas failure information on the vehicles tested. The intent of this paper is to present the results of this study.