I think I figured it out.

I found an excellent article explaining TPMS in detail here: http://www.aa1car.com/library/tire_monitors.htm
And within that article was the following that is probably what happened to me:



Problem is, I've been in many situations where the Fix-a-flat products have saved miass, including a trip with my 4 yo son where we got 2 flat tires a long way from anywhere. I'm also rather surprised they couldn't tolerate that stuff considering the extremely harsh environment inside a tire. (Shock, vibration, extreme cold & heat, moisture . . . )

32 bucks is the cheapest I've found so far: http://www.tpmswholesalers.com/Sensors.aspx
Schucks/Oreilly can order them (2 days out) for $51. I haven't bothered calling the stealer.

PROBLEM: Finding a shop that will install them. 2 shops so far said they won't install a customer supplied part - - - and if they ordered the part, it would be from the stealer.

If possible, I would like to try and reset the system first and see if that helps. This is what I've found so far on how to test them:

TIRE SENSOR 2 LOW PRESSURE ALERT
² When Monitored:
Continuously.
² Set Condition:
The fault is set when there is a low tire pressure condition or sensor pressure measurement failure from the sensor/transmitter.
Possible Causes:
INTERMITTENT PERFORMANCE DTC
INCORRECT TIRE PRESSURE
TIRE PRESSURE SENSOR
WCM (SKREEM)

Theory of Operation
The tire pressure sensor actively monitors the air pressure and air temperature inside the tire, the sensor internal battery status, and the radial acceleration of the wheel. Each sensor has a unique ID code. The sensor transmits the data at regular intervals via an encoded signal to a receiver circuit located in the Wireless Control Module (SKREEM).
² When Monitored:
With vehicle speed greater than 15 m.p.h. (24 km/h).
² Set Condition:
The WCM (SKREEM) will monitor the signals from the four active road tire sensors. A loss of signal error is detected when eight consecutive blocks of data are not received or cannot be accurately decoded. An internal sensor hardware error condition will be set.

Diagnostic Test
1. DTC STATUS IS ACTIVE
NOTE: If the incorrect Placard Values (??) were programmed into the WCM/SKREEM, a DTC could be set. Before continuing with any TPM diagnostic test, using the scan tool, check that the correct Placard Values have been programmed in to the module.
NOTE:
If the following conditions are present:
– Low Tire Pressure DTC (Stored)
– Tire Pressure Sensor Internal DTC (Active)
– Spare Tire is not equipped with a Tire Pressure Sensor
– Spare Tire is currently on the vehicle
Repair the tire and place it back on the vehicle.
Test drive the vehicle.
If the DTC(s) reset continue with the diagnostic procedure.
Turn the ignition on.
With the scan tool, select View DTCs in the Wireless Control Module (SKREEM).
Is the DTC status Active at this time?
Yes >> Go to 2
No >> Go to 4
2. TIRE PRESSURE SENSOR
NOTE:
When working with vehicles equipped with the base tire pressure monitoring system the correct tire that set the fault must be identified. Following the below procedure will help in identifying the correct tire.
1. Set all tire pressures to the recommended specifications and recheck for fault/alert.
2. Turn the ignition on.
3. Starting with the left front wheel, deflate the tire to 20 PSI and wait 2 minutes. The fault will set once the
pressure has reached 20 PSI within the 2 minute time frame.
4. If the TPM fault was detected and not associated to this Sensor/Transmitter, repeat the process until the faulty Sensor/Transmitter has been identified.Once a fault/alert has set, it will establish the location of the tire pressure sensors/transmitter. Repeat steps until the applicable Tire Pressure Sensor/Transmitter has been located.
Turn the ignition off.

When mine was broken because the tire store put on a metal cap and tightened it too tight causing the valve stem to break on removal all that was necessary was to unseat and remove the outter bead. That allowed the sender to be replaced and the bead put back on without moving the tire position on the rim that would have then need rebalancing. A friend owns a repair shop so it cost me a dozen donuts

BE VERY CAREFUL WHEN TIGHTENING THE NUT ON THE VALVE STEM. IT'S PLASTIC
The torque setting is very low, inch pounds, and it didn't really even get tight