I had a similar doubt with my 2009 997.2 C2. Although the TPMS was working as it should, I decided that when I ordered my full set of Michelin Pilot Sport 4S tires from COSTCO it would also be a great time to change the sensors since I presumed that they were the originals.

I ordered a full set from these folks which at $119 is a steal ( https://www.tpmsdirect.com/Porsche_9...08-05-hufm.htm ). They are Huf brand which I believe is what Porsche uses and then sells with a ridiculous markup because they have the Porsche logo. BTW, the folks at COSTO was nice enough to remove the old and install the new for free. As expected they worked as expected and provided the pressure readings after driving only about a mile.

 

The problem is fixed (for now).

The car had 18 inch wheels when new back in 2006 and were replaced by the previous owner with the 19 inch wheels and tires.

When I bought the car, my after market dealer inflated the tires to the specifications that were in the front door panel which were too high and based on the prior 18 inch wheels.

This morning, the dealer reset the sensors for the appropriate 19 inch wheel specifications and inflated the tires to the appropriate pressures, 33 front and 39 rear and now the TPMS system is working properly.

This system is very temperamental indeed.

 

This is what I did:

https://rennlist.com/forums/997-foru...ing-level.html