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Discussion Starter #1
For the second time in less than a week now I got a cel for a p0128, when it comes on the temp readout on the dash just displays "---" and the fans kick on high and stay on. I have my aero force interceptor gauge plugged in and monitoring the coolant temp and it works perfectly fine and seems like the temp is normal even when the code pops up. If I clear the code, everything instantly goes back to normal like there was never even a problem and it is frustrating!
Really want to get this figured out before I put the supercharger on this weekend, anybody have any idea what is going on?
 

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Well, it looks like you already know what the code means, but just for future reference:

P0128 Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
Maybe a bad sensor? Is your aero force attached to the stock sensor?
 

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Well it just pulls the data from the obd2 port so yes, that's why I'm so confused by this.. this morning it popped up after 3 miles and the temp was at 183 when it happened..
 

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I assume you've also made sure it doesn't need to be changed, right?

Looks like a faulty air intake temp sensor can cause it. I assume our MAF has one of those, but I honestly don't know.
 

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Discussion Starter #7
IAT seems perfectly normal as well, that's the other thing I have the interceptor displaying haha, and the coolant? It's still good, it was changed shortly before I got it but I planned on flushing it out in the springtime
 

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Hmm, well that definitely makes it puzzling. I'm all out of ideas... and so is Google, haha

Maybe you'll find something after you log all the data on your laptop!
 

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The rubber gasket probably folded over and is letting coolant by not letting temperature come up fast enough. You just need a thermostat.
 

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Well then I guess I'll try that then haha, how hard is it to get at the thermostat on these things anyways?
Not too hard at all you might want an extension for your socket wrench. It's just 2 bolts either 9mm or 10mm and the thermostat lifts out, just have something to catch the coolant that comes out unless you drain the system first.
 

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It looks worse than it really is haha. You might have to push a hose or wire harness out of the way but if you have an ~8" extension for your socket wrench it isn't as bad. Just reaching down to get to it might be hard if you have big hands.
 

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Discussion Starter #17
I'll get it haha, one of the easier things I'll be doing to my car over this 3 day weekend...

---------- Post added at 11:15 PM ---------- Previous post was at 10:28 PM ----------

It's getting worse I guess, temp wouldn't even reach 170 on my way home tonight
 

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My 2007 had a similar problem -- it was not the coolant temp sensor. New Thermostat fixed it. The rubber gasket where the thermostat seats was deformed and partially shredded. I purchased the AC Delco T-stat online from Rockauto --p/n 131-158, GM#12622410. Not a bad job -- need a long extension and a catch-pan for the coolant.
 
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