97 Deville - Code P1258

Need some help here. I have a 97 Sedan Deville with code for P1258, Engine Over temp protection. The car does not overheat, but the idiot light will come on and in the information center will display vehicle overheated, stop and idle. I have replaced the thermostat, ECT, removed radiator and have flushed, PCM (used but had reprogrammed to correct vin), and dash. With the ect disconnected, I ran the car for 6 minutes and the temp on the dash rose 11 degrees and the startup ect temp rose 22 degrees. The ECT Startup temp is at minimum 100 degrees more than what it actually is. From my research, i found the pcm interprets temp from ect, and then sends it through the serial data line to I/P. So where's my problem?......

i fixed my own problem. the new thermostat installed was bad.