I'm sure it's not the heater control as that's bigger but slimmer if that makers sense !! and mines located next to the ecu it's about half the size of the ecu .I know it's heater controls because I had none for years the minute I fitted it all the heating controls worked :lol:.Its on the passenger side behind the ash tray .it fixes to the rollbar up behind the glove box, i think its for or the heater controls and the little black box does the calculations