Short Test Results on 1980 and 1981 Passenger Cars from the Arizona Inspection and Maintenance Program

This paper presents the results of a study which examined short test results and repair data on 1980 (GM vehicles only) and 1981 (all makes) model year passenger cars participating in the Arizona Inspection and Maintenance (I/M) program. The primary purpose of the study was to gather information on the failure rates of these vehicles using the Arizona short test, their mean emission levels, and the types of repairs performed on the failing cars. A unique part of the study was that a generalized software system was developed to extract very specific emission control information from the vehicle identification numbers (VIN's) for these vehicles. The results of the study indicate that in general these vehicles have quite low failure rates in comparison with pre-1980 vehicles, and that certain vehicles have a higher probability of failing the short test than others. The results also indicate that 80−90% of the failed vehicles are successfully repaired by service personnel, and that the average I/M repair cost for 1981 vehicles when free (warranty) repairs are not included is around $38.