The best scanner you can find that is compatible with an iPhone is no doubt the OBDLink MX+. This device turns iPhones into professional-grade top rated obd2 scanners, able to do just about everything a wired scanner can. The best thing about this Bluetooth OBD2 Device is that it is optimized for both Android and iOS operating systems for phones. What makes it the best for iOs is that it comes with a free app, without any hidden fees or annoying in-app purchases.