A systematic method and system for testing the charging and starting systems of a vehicle, which requires each individual test to pass before proceeding is provided. In addition, the invention incorporates an improved alternator test that determines whether the alternator belt is slipping using data read using a vehicle data port. Further, the invention provides a battery bank test that correlates the voltage before and after a load is applied to the battery bank to the batteries' conditions. When testing the starter, the oil temperature is read via the vehicle data port, allowing for a determination of whether the current draw is abnormally high.