Took my '97 C5 out after it had sat for a couple months and got a DIC message that said "left rear tire flat". Had checked tires before driving, but stopped and checked and tire ok. Hit the reset button and pressure on display came up "1". Continued to get the message and then it changed to "service TPM system". Could a bad tire sensor be the problem or something electrical? Could not find anything the the owner's manual about re-setting the system.

Dave

 

I found an article on re-programming tire sensors with a strong magnet, including the steps to re-programming the system. Will give this a try and see if it works. If not, sounds as if I have a bad sensor. Dave

 

...or it needs a new battery.