I've used OBDII code readers for a number of years now and find them indispensable for figuring out why your car's check engine light is on.The INNOVA Electronics Fix-Assist 3130c takes performs that task perfectly, as well as offering suggestions for car repair based on the codes it reads from your car engine. It is a complete mechanics tool, offering scan and report for everything your car computer can report, including a LIVE mode - an engine running monitor that graphs out performance of the engine while you put it through the paces.The unit requires 3 AA batteries and has a backlit, white display. It also comes with a USB cable so that you can connect it to your computer and get further information about repairs.You can record trouble codes from a cleared state, triggered on the DTC code getting set or a manual trigger which can really help if you are trying to figure out any engine code issues. The scan with ignition on and engine off gets any set error codes or conditions, but the real excitement is using the tool to examine the engine load parameters, or resetting those bad codes and watching the engine while they pop back up. The unit also has special tests for the O2 Sensor, EVAP leak, and power train systems that are not continuous monitor.This unit will allow you to understand a bit more about any issues they are having with a modern OBD2 equipped car before they visit their mechanic to discuss any repairs. You can also be certain you don't have emissions problems before you go to the inspection station. In fact, many states they use similar OBDII code readers to 'Pass' your car for emissions testing.The unit worked perfectly for me - correctly identifying both cars I connected it to.My biggest problem with this code reader is that to get the full functionality of this fine machine, you must pay almost $60/yr fee per car. That is not advertised on the packaging and I don't care for those kinds of hidden fees in a product that is already somewhat expensive. For a two car family, that's $120/yr and unless your cars are older and you will be doing your own repairs, it might be more cost effective to buy a regular scanner (without Fix-Assist) for around $30. However, if you often do your own repairs, this is an extremely valuable tool and definitely worth the money.I also think that for the price, a full printed users manual should have been included. Instead, it is available for download on the INNOVA website.This is a great automotive accessory you can get for any car (built in 1996 or newer) to help you understand your machine and survive modern auto repair with your wallet intact. It is an easy plug and play system, even for people with no automotive background, and I give it 4 stars.