what is code p 1351

This is a Variable Valve Timing or VVT code. If your timing belt is loose or has been replaced recently, it means that the belt could be off a tooth. Also, if your VVT Solenoid screen is dirty, possibly from infrequent oil changes this can also set this code. It may show up in reverse, because there is a different torque being applied. Last thing is to look for is a wiring harness that is being stretched when in reverse, possibly due to a worn engine or transmission mount.