I have had this problem now for months, all my tires are properly inflated and no light ever comes on on the dash, the DIC message "Service tire monitoring system" comes on all the time. I just click it off and call it good.
As far as I am concerned, this system is not needed anyhow as long as one regularly checks the tire pressures. I mean, it is like having to wear a helmet on a bicycle, I never did and I am still alive. Things just get more and more complicated because of the peeps that do not care about being proactive and check pressures regularly.