There are two TPMS systems, base and premium. The premium has always provided tire pressure. Base just an indicator. They use the same wheel sensors regardless, but the STR8s are little different.
You will get a chime and a flashing indicator when first starting up, the indicator goes solid after awhile, no other chimes. Some have reported that after several drives the TPMS just gives up and doesn't bother with indicators.
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac