The engine B1684 Code has different meanings but for a single car, the code has one meaning. You have to get the manufacturer name and model number to identify the problem. The valves of individual cylinder are reserved locked using a pair of arms that replace the conventional engine’s roller-type rocker arm. B1684 code one of these arms follows the cam profile while the second arm connects to the valves. During normal engine operation, the 2 arms are combined by a locking pin. If you have all expensive tools and machineries as well as you know all information, you can solve the problem in your place.