Thanks for confirming the year break in the progression of the system, Daryl! I was aware of the fact of a break, I just couldn't remember when.
That's why I just tossed it out as a fwiw. The no DTC was what got my attention in this case as it's exactly like my symptoms. My diagnostics were easy as I have the OEM tires & wheels & sensors for my car still intact & I know that they worked (no lights on DIC). I do believe that if the "battery" gets stuck, it minicks a "intermittant fault" and doesn't set a hard code. I say that because the light goes out upon shut down & restart. Or in my case, it goes out if the "battery" decides to come back from coffee break!
My wear theory is bassed upon our "How To" section and the fact that my OEM stuff only had like 8k miles on it in almost 15 yrs. I bought three NOS sensors and the right front replacement was from a salvage yard with 40+k miles, or at least that's what they said....
....and that's the one with the worn battery track, and it's the one setting my service light.
I should look up the system in my 08 Cobalt's FSM and see what is different? I wonder if they changed the power supply???
