P0128 on a 2001 TB

My SES light started today. I had the code pulled off it, was P0128 Collant temp Below Thermostat Regulating temp. This would seem to indicate a bad thermostat however, the temp gauge reads normal (210 degrees) the heater itself works fine. and the fluid level is perfect. Anyone ever run into this. Given the lack is temp issues I am beginning to wonder if the sensor isn't hosed. If so anyone know the name of the sensor that would cause this issue?

It is possible there are 2 sensors, one for the gage and 1 for the computer, not sure here, the temp sensor for the pcm could be bad or open wiring to it. I asssume this is the old style TB with the 4.3 v6, not the Trailblazer of new. If so the right forum would be Blazer, but I am now sure about the 2 sensors, seeing you have a 2001, which is the s-10.

It is possible there are 2 sensors, one for the gage and 1 for the computer, not sure here, the temp sensor for the pcm could be bad or open wiring to it. I asssume this is the old style TB with the 4.3 v6, not the Trailblazer of new. If so the right forum would be Blazer, but I am now sure about the 2 sensors, seeing you have a 2001, which is the s-10.
Man, I need some sleep, it is a 2002. I actually have the "new" Trailblazer (with the straight 6), it was the first year they made them so I have had all the bugs to fix :( . I was watching the temp gauge this morning on the way to work (25 miles) and it was VERY slow to rise. Never reached 210. Usually it heats up very fast hits 210 and stays there. So I am starting to think replacing the thermostat may be the way to go.
I don't work for them but I have to tell you guys, the fellas at Advance were awesome. I had no idea they checked those codes for free. Last time i had to pay the dealership $70 to get the code.
Anyway, thanks for the quick reply man. I really don;t know how I'd figure some of these codes out.

Yeah do the thermostat, keep posting here you will find some good help just be careful with AZ selling unnecessary parts the scan.

I am having a similar problem... the temp gauge is very SLOW to rise, but never gets past the first 1/4 click. I was told it is probaly the coolant temperature sensor and not the thermostat. Apparently the sensor tells the thermo how much to open, but if there is a problem with the sensor, the thromo stays "wide open". It was -10 degrees here last week, and the temp gauge never went above 110*. (BRRR... thank god for those butt warmers!)

Does anyone know where the sensor is, i am going to try that 1st, because the thermo is burried behind the PS pump, and probably not that fun to replace!

I do not believe the the thermostat is electronically controlled. Replace it.