There is provided a method for improving maintenance diagnosis using maintenance repair data from previously maintained vehicles. Maintenance repair data from previously maintained vehicles are obtained from a storage device. The maintenance data are compiled in a maintenance diagnostics data set and a maintenance work code data set. The maintenance diagnostic code data set and maintenance work code data set are categorized into an electronic data table. Respective combinations are formed in the electronic data table. A total count is determined for each respective combination in the electronic data table. Either a respective diagnostic code or a respective maintenance operation code having a correlation of more than one of either maintenance diagnosis code or maintenance work codes is identified. which is used to repair the vehicle, a maintenance repair procedure, and / or which is used for identifying the error, a respective maintenance diagnostic code are modified in response to analyzing the respective combinations.