You have to solve the problem of the car engine and this B1646 Code comes while the car is diagnosed. It seems that body of the car has the main problem and you do not need to pay huge amount as inner side of the engine has no problem. Do not try to solve the problem in your place. You have to know the dictionary meaning as well. The dictionary meaning of the car gives you some information for solving the car problem easily. When you will get the car after fixing, you should take car for test drive and if you get any problem, then let the engineer know about it.