On the JK, the speedometer can stop working if a module on the vehicle doesn't update properly during programming.  This can be caused by:The key not being in the on position with the engine off during programmingTurning the key off during or quickly after programmingNot turning the key off after programming before starting the engineBad luck by trying to program when the Jeep is doing internal regular updates.Luckily the fix is easy:Clear the codes in the DTC tab by tapping on the codesCycle Ignition off then back on without starting the engineProgram a size that is at least 1/2" different than the current valueCycle Ignition off then back on without starting the engineProgram the correct sizeCycle Ignition off then back on without starting the engine