[f5fstop]

Not sure if this is your problem, but it is a problem for many people.
The system is set to signal a low tire if the reading drops below 25-26 psi. So, let's say at night you have one tire that is reading about 28 psi, and overnight, the temperature drops 20 degrees, the next morning when you start the vehicle, the system may determine you have a low tire. Every 10 degree drop in air temp, drops the tire pressure by 1 psi. So, at night you have 28 psi, but in the morning you have 26 psi.
Now, you drive to the dealer, starting with the tire at 26 psi. However, the tire warms, the pressure goes up, and bingo, the message goes away. The system is not smart enough to know the increase in pressure is due to driving, it assumes you added air.
So, I would check the pressures on cold tires that have been parked in the shade (Cold tires=tires that have not been driven for over three hours.) Then adjust the tire pressure in the tires to match what they should be per the tire placement label.
Again, make sure one side of the vehicle is not in direct sunlight. Sunlight directed on the tire can cause the air pressure inside to increase by up to 3 psi, depending on the condition.
This is a large problem facing many auto manufacturers today and will become larger as more tire pressure monitoring systems are added due to Federal regulation. For years, many customers have never checked their tire pressure, and they do not understand the relationship of tire pressure versus heat/cold cycles. Dealers are swamped some mornings with customers who drive in with a message that one of their tires, or all of their tires are low in pressure.
Again, I'm not saying this is your problem, but it is a large problem with the population at large.
If this is not your problem, then I can't say. Impossible to troubleshoot an electrical problem without being there.