My 2002 Xj8 has the amber light on dash and is throwing a gearbox fault and is sluggish until the car itself warms up, from there I turn the car off and back on and it drives smoothly with no fault any ideas upon what the problem could be? The current code that's related to the gearbox is p0743 thanks.

 

DTC guide for the X308 and X100 4.0.