The B1645 Code is related with the car engine. You need to get the accurate meanings of the engine for solving the problem of the engine. You cannot use this car with the problem. It is better if you hand over the car to a professional person who can solve the problem as soon as possible. The engine system, in conjunction with the engine control module or powertrain control module, triggers the B1645 code solenoid valve to regulate oil pressure to the engine mechanism that is connected in the valve system to switch valve timing amid Low and High. If the engine solenoid valve has a short circuit.