You are getting Lacie code 43 error when you connect the Lacie external hard disk to the Mac. The system will not recognize the Lacie drive and ask you to format. This may be because of the hard drive corruption. The corruption can be due to improper disconnection of the drive from the system or abrupt shut down of the system. There can also be some file system corruption, volume header corruption or any type of virus infection. First you should check the drive by using the disk utility present in the Mac, if it is unable to solve it the only way to fix Lacie code 43 is to format the drive to the recognizable file system. This will remove all the corruption issues and also it will erase all the data of the drive. The data can be recovered after fixing Lacie code 43 with the use of time machine or if you have a personal backup. When the backup is not present then you can use the Lacie drive recovery software when the Lacie code 43 is solved. The software has simple process of recovery and you can restore your data efficiently.