I think if you unplug the motors, turn it on and off then plug back in, it will do a calibration.
If you turn the engine on with the external temp sensor unplugged, it shows -35c. If you switch off then plug it back in, it takes ages to get back to the real temp and pauses the sync back to normal while the ignition is off, inferring it has a memory. Memory persists even when the battery is disconnected. This suggests the calibration counter might also persist
That said, I've heard it do a calibration at less than ever 500 cycles so there must be some way to reset the counter