Cel. P0128

[digglesworth]

Well the cel came on today so I stopped into the local AutoZone to get it read. Came up with the P0128. I guess that's something to do with the coolant temp. Ive been meaning to do a coolant system flush just havent gotten around to it yet. Looks like I'll be changing the tthermostat and coolant temp sensor when I do it... Anyone else have the same issue.? Any insight would be appreciated...

 

[ArtHummer]

If it's not overheating most likely is the cooling temp sensor.

 

[digglesworth]

That's likely the culprit. I always hear stories of the H3 running on the hot side but mine has never really rose above 1/2 on the gauge. I understand it's just a guage and isn't 100% accurate... But I'm not seeing a spike in temps so I'm assuming it's just the sensor. I'm not super psyched to swap t-stats cause it seems like the location makes it a pain... Any idea where this sensor is located...? For now, I just disconnected the battery cable to reset the light and I'll change the sensor soon.

 

[ArtHummer]

It's on the right side of the head all the way on the back.

 

[Happy Hummer]

https://sites.google.com/site/happyhummer01/thermostat--cts-replacement

a write up right here go to this spot thanks Chris

 

[digglesworth]

Thanks for that link... I'm really not looking forward to changing any of that out. Looks like I better clear out a whole weekend...

 

[Steve #1]

My experience with it was that the thermostat was stuck open which is probably your issue if you aren't over heating. With the engine cool, start it up and grab on to the radiator hose and see if it gradually gets warm or if it stays cool then suddenly gets hot. As long as you accept the fact that you will make a mess and you have the right combination of socket extensions, changing the thermostat isn't that bad.

 

[digglesworth]

The sensor looks like it's gonna be a booger... I'm no stranger to contorting myself into some circus-like positions to get in engine bays... I picked up the sealed funnel that screws on the radiator to burp all the air out of the system. Now I just gotta get around to knocking out my giant to-do list.

 

[poncho1965]

I pulled the front drivers side wheel liner to get to the thermostat easier. 2 hours or so to do the job.


Mike

 

[nrinzema]

Just had the p0128 cel myself, new thermostat and so far no cel!

Sent from my SCH-I605 using Tapatalk 4

 

[digglesworth]

Just had the p0128 cel myself, new thermostat and so far no cel!

Sent from my SCH-I605 using Tapatalk 4

Did you notice any change in where your temp gauge sits afterwards? I'm thinking mine is running cool cause the t-stat is stuck open. After I change it, I'm thinking it will let the engine warm up to what normal operating temp should be.

 

[poncho1965]

Mine was not climbing above 1/4 of the way. I kept clearing the code and it kept coming back. Funny how you don't notice the change, I just figured it was because it was winter. The scangauge will make things easier from here on out.

 

[digglesworth]

That's exactly what mine does... It only got up to the halfway point in the dead of summer when it got unto the 90s.

 

[nrinzema]

Did you notice any change in where your temp gauge sits afterwards? I'm thinking mine is running cool cause the t-stat is stuck open. After I change it, I'm thinking it will let the engine warm up to what normal operating temp should be.

It would not warm up above 1/4, now it will easily warm up to up to 1/2. Other than that no change on the temp guage.

-Nate

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[alrock]

I would agree with Steve that a bad thermostat is a very likely cause of the issue if the engine is not getting to 1/2. Thermostats can fail either open or closed, and if they fail open the engine doesn't get to normal operating temperature. The biggest issue with that, I believe, would be a possible loss in mpg.

 

[digglesworth]

Loss in mpg you say..... Wow... I get 16.5 to 18.5 depending on how much city I mix with my highway. That'd be fantastic to get another 1-2 outta ms. piggy.... Any other adverse effects to not getting up to spec'd normal operating temp? Also, I bought some Prestone radiator flush to use to clean out the system. If my t-stat is in fact stuck open, should I run the flush through before or after replacing the t-stat?