Is your check engine light on? Is your car making a weird noise ? Is your car no behaving as usual ? Are you buying a used car and want to check the codes before buying? An OBDII scan could give you an idea of the mechanical state of the engine and other components of the car. If your check engine light is on it could give you the exact reason of why the light is on. I bought an ODBII scanner when i bought my car and only had the occasion to use it a couple of times. It is quite an expensive tool to buy and I would love to use my investment to help others ! I am not a car mechanic by any means but ODBII codes can help you figure out if the car has engine problems or computer problems before you go to the garage and throw a bunch of money at them. Sometimes the check engine light is on because of really weird and simple reasons like not screwing the gas cap properly. An ODBII scan before going to the garage could save you a bunch of cash.