There is a well known issue with a spice in the loom that can give the same effect (usually gives a check engine light signal). Axe has the directions to fix it.

Also could be a dirty contact to the temperature sender to the ECU (different to the gauge sender but located nearby on the water pump housing (when cold the engine will not lock-up into 4th gear, dodgy signal could be fooling the ECU). Clean both sets of terminals to be sure.

2002 Sporty , Ironman 2.5" spring, 2" body, 15 x 7 ROH wheels, K&N, 15 x 10.5 Simex Centipedes, Powerchip 91.

"Never argue with an idiot. They will bring you down to their level then beat you with experience!"