Even though I cannot be 100% certain, unless the circumference of your tires is different than the stock tires, I don't believe your 19" tire size would make any difference in the system detection of a low tire pressure condition, since it is monitoring the input signals from all four wheel speed sensors to make comparison and determine if there is a tire low on pressure. From what I can understand, the system is learning the inputs from the sensors over a period of time to determine what is normal input. Then if it detects deviation from one of the sensors, it turns on the warning light. (A simplified description).
To reset or re-initialize the system, you have to initially push the reset button to turn off the light if it is on, then push and hold the button until the light blinks three time. After than, the vehicle needs to be driven for about an hour above 20 mph to complete the initialization.
N.E.O.