Don't forget that when the tires warm up you will pick up a couple pounds of pressure from heat expansion.As it turns out the shop that did my last tire rotation must have also reset the sensors. I reset them last night and the same low pressure lf appears. This only lasts until the tires warm up then it shows the same pressure as the rest, except for about a pound. Sensor must be going.
The battery is not a service item. It "might be" possible to replace the battery but GM only sells the complete sensor.Those things have a lithium battery installed. Of course, they have a finite lifespan. Anybody ever replace a battery, or do you have to replace the whole sensor ???
You might check the service documents if you can; sensors were more like $40 to $50 last time I checked.I had a sensor replaced a year ago. I believe it was less than $10, to my surprise.
Do everything you can to be sure this 'service station' operator remains in business! You have found someone who cares about your car and your future service needs. Rare.When I had my tires rotated, they must have reset the sensors without telling me, because the readings were still accurate. This was all at a service station, not a dealer.