GMC thermostat

John-MI

Member
Does anyone know if a bad thermostat will cause a check engine lite to come on, or was it just a coinsendence. It's a GMC 2000 model V8.
 
Absolutely, you will get a code if engine does not come up to temperature, and would assume if it overheats.
 
Yes, if it is stuck open not letting temp stay above a minimum. Code po128 is a common one, or a po126. Wont set a code if stuck closed however, computer has no way to know that.
 
Both my gmc truck and biuck had defective thermostats with under 50k. Both had chech engine and in the winter neither would keep me warm.
 
When I have to replace the thermostat I replace it with a failsafe thermostat.If they stick they stick in the open position so truck or car won't over heat engine. The auto supplies around here call it the women thermostat.
 
beety, you need to read up on how the "failsafe" thermostats work.

If they fail CLOSED, as many thermostats do, there's no "failsafe" mode.

The way the failsafe function works is if the engine gets grossly overheated for some reason other than the t-stat (with a working t-stat) and the t-stat opens more than normal, a latch mechanism grabs it so it can't close.

SERIOUSLY, that's the way it is, pretty much marketing hype.
 
Those things are junk! Every one I have used has failed within 3 - 5 months of putting them in. The problem is, lets say you have a 180* tstat. Coolant gets up to 185, tstat is stuck open! No way to fix it, other than change it. A regular tstat wont do that. And you wont get a replacement for free under warranty, it did exactly what it was suppose to do!!
 
(quoted from post at 04:29:00 10/24/14) Yes, if it is stuck open not letting temp stay above a minimum. Code po128 is a common one, or a po126. Wont set a code if stuck closed however, computer has no way to know that.

PO128 = Takes to long to get to operating temp inside a certain time frame... The puter will set a code if the engine overheats....

128 is a quick kill code unless its a Honda,,, If you go for the quick kill on a Honda it will be back at your door in a few days with the same code :cry:
 
Who cares if you don't get free one at least you haven't ruined an engine from over heating.Comes in real handy when wife drives because all they do is drive they never watch gauages no matter how hard you drill them. I have been using them for years and haven't had any problems with them. The one in my GMC has been in it 10 years. When I buy a thermostat I buy the top line never a cheapo's.
 
I care! But I see what youre saying. And uh, my wife does pay attention to her gauges, n fact better than I do I admit. My point is, I would expect to get more than a few months use of a thermostat. Anything can fail, but my experience with the Failsafe is they are, in my opinion, junk, that has cost me more money to use than a Stant, or factory tstat. I will not use a "store brand" tstat. BTW, my experience with the FS tstat has been in Fords and one Dodge, so maybe the design is better for GM vehicles.
 
Sons hung open TWICE. First one was in traffic, second did it sitting in the yard after coming home from school. Doesnt take much overheating to expand enough to catch. For giggles I got the lock loose without damage, put it in water and got it up to 196 by my therm, and it has stuck again. Its a 192 tstat for an 03 Ford Ranger, and was less than a month old. So on his, it didnt take much.
 

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