Had all three of these happen on my way to work this morning on my 01 Monte SS. Checked the code at Auto Zone. I think it was a P0128 but can't remeber for sure. Guy told me it was for coolant level below sensor level. Fan running after engine shut off, Temp guage not moving off the bottom. I checked the radiator fluid and it was full in the bottle an in the radiator. So I figured I had a bad thermostat. Replaced it. Started the engine, bled off the air top off the antifreeze.About three ounces needed. Temp guage moved right on up where it should. Check engine light still on. Tried disconnecting the battery to clear the code. Did not work. Light still on. Could this be a latched code? I've seen some OBDII codes latch until so many starts before going away. Any ideas? By the way. It was a semi cold day here in Dallas today. But not that cold.
Thanks in Advance!

 

Sometimes if you leave the battery disconnected overnight it will take care of the code. I suggest going to autozone and have them clear it for you. I had a similiar problem in my monte and I went ahead and replaced the t-stat and temp sensor while I was in that area.

 

u didnt leave the battery disconnected long enough...take it off for at least 5 minutes

 

Next time I'll try leaving it off longer. I had it off for maybe ten minutes. Code cleared itself the next day. So I guess this is a latched code until the problem is corrected and the ignition is cycled on and off a few times. Every time I've tried getting Autozone to clear a code for me they said that the machine they use is not capable of doing that?

 

I had the same problem with my 2001. Temp gauge quit working. I figured either the sending unit or instrument cluster. Tried sending unit first hoping it was'nt the cluster, didn't work. I also noticed later, when it got warm enough, that the A/C didn't blow cold. Worked fine before. Took it to a local service center to check the A/C, and they said everything was OK except the compressor was'nt comming on, probable electrial problem. I thought maybe a breaker. Not knowing what else to do I was going to replace the breakers and hope for the best. I had been to the local Chevy dealer earlier today for the recall on the engine bay fire issue so I figured I would go back and ask if they knew of any other areas that I might need to look at. They ran a scan, several temp codes showed up. They cleared the codes and my temp gauge and A/C worked great. They told me I needed to replace my t-stat. Apparently, if the t-stat is stuck open, the engine does not reach proper temp. it trips a code and goes to default. Who would've the a t-stat could cause such problems. Will change t-stat and radiator cap tomorrow. Will let you know if it solves problem