Auto box limp mode

[Solboy]

Hi everyone. After fitting a used engine in my 2004 auto galaxy the gearbox is in limp mode. I had it read and it says speed sensor is faulty even though it still reads the speed on the speedo. Has any one had this problem before could advise me. Many thanks

[Chrispb]

Hello 

If it was OK before the change have a check of the wiring multiplug and condition of wiring (corrosion and breakage)