[Bobby Boucher]

I am posting this because even though I found plenty of P0128 code threads, none were exactly like my problem. Hopefully this will help someone out. Sorry ion advance if I posted this in the wrong spot

08 Chevy 'rado, I-5, auto

What happened​

Temp gauge turns off, needle rests at the off position
A/C OFF in the info center, so no more air conditioning
This happened on and off all summer
Finally throws a code P0128 (coolant temp below thermostat regulating temp)

How I fixed it​

For those that don't know, the truck will shut the a/c off automatically if the engine gets too hot. Initially thought it was a thermostat problem, but this would not explain the temp gauge failing also. Replaced the coolant temp sensor, cleared the code and so far the problem has not come back. This makes sense, when the sensor acts up it turns off the temp gauge, and when truck realizes it doesn't know the temperature of the engine it shuts off the a/c just to be safe.
This problem would come and go for weeks at a time, time will tell if it's been solved but so far so good.

 

[08Canyon]

Re: P0128 Solution

Is what you are saying is that you had trouble code P0128 and you changed the coolant temp sensor and so far it appears to be the fix?

 

[Supermodulation]

Re: P0128 Solution

The 2008 models were plagued with electrical connector problems after GM decided to use CHINA made electrical connectors. The pins would back out of the connectors.
Solution was to push the pins back in.

Also check both inner fender grounding blocks. These are notorious for causing electrical gremlins.

 

[Bobby Boucher]

Re: P0128 Solution

Is what you are saying is that you had trouble code P0128 and you changed the coolant temp sensor and so far it appears to be the fix?

Yes.

The 2008 models were plagued with electrical connector problems after GM decided to use CHINA made electrical connectors. The pins would back out of the connectors.
Solution was to push the pins back in.

Also check both inner fender grounding blocks. These are notorious for causing electrical gremlins.

Good to know. Hopefully ac delco makes a sensor that lasts

 

[Undead Rado]

Re: P0128 Solution

If it comes up again I would change the thermostat. If it's not getting up to temp (stuck open) you may drive several miles before it throws again. I had the same thing going on a few months ago, ac might work for days before it threw the code, when the code throws it automatically stops reading temp, whether the sensor is good or not, and shuts off the ac

 

[Joe canyon]

Re: P0128 Solution

Was the plan to have people throw parts at this problem, or perhaps multiple triips to a dealers service department? In fact why have a temp gage for the driver if it is inaccurate or just stops working? Glad op followed up on a solution to a multiple symptom fuckup in engineering.

 

[08Canyon]

Re: P0128 Solution

Was the plan to have people throw parts at this problem, or perhaps multiple triips to a dealers service department? In fact why have a temp gage for the driver if it is inaccurate or just stops working? Glad op followed up on a solution to a multiple symptom fuckup in engineering.

What part of it was a design flaw?

I don't get it....

 

[Undead Rado]

Re: P0128 Solution

I changed the temp sensor or mine first thinking it was bad, new sensor no change, cut out the plug and hard wired it, no change, actually watched my temp gauge and seen it wasn't getting up to temp so I wasted $ on the temp sensor when it was the thermostat the whole time, but my ac blower resistor baked at the same time so I thought I had a short somewhere

 

[Joe canyon]

Re: P0128 Solution

What part of it was a design flaw?

I don't get it....[/QUOTE

So what else is new o8 the problem needs addressed. I don't think realise the serious complications this could cause someone.

 

[08Canyon]

Re: P0128 Solution

But what problem? Most of the time it's a thermostat. If so far your sensor has fixed it, it seems like you're the only one.

Do you mean a faulty sensor is the engineering flaw?

Thermostats don't last forever, so that is not an engineering problem.

 

[Bobby Boucher]

Re: P0128 Solution

Seems like an engineering flaw, the sensors appear to be cheap. I thought it was the thermostat for sure, until I talked with some mechanic friends that suggested otherwise.

In fact why have a temp gage for the driver if it is inaccurate or just stops working?

I find the gauge pretty useless, even when it shut off I just listened to the engine. I'll trust my sensors before a faulty sensor. I miss the numbered gauge on my WJ.

 

[Rick_crew]

Re: P0128 Solution

Was the plan to have people throw parts at this problem, or perhaps multiple triips to a dealers service department? In fact why have a temp gage for the driver if it is inaccurate or just stops working? Glad op followed up on a solution to a multiple symptom fuckup in engineering.

All manufacturers have service problems caused by poor choice of suppliers.
Usually it's because the supplier offered the best price, but sometimes it's just that the supplier made a mistake somewhere along the way.

ALL auto makers experience this at one time or another.
Sometimes it's a small inexpensive component that over the span of production for a particular vehicle causes major reliability problems.

 

[Joe canyon]

Re: P0128 Solution

I'm sure they were aware of the potential problem as it is not just a 355 platform only incident.

 

[Bobby Boucher]

Re: P0128 Solution

Update

Turns out replacing the temp sensor did NOT solve the problem. As soon as it got cold my gauge started acting up again, so I swapped the thermostat and that did the trick. The problem has not come back since November when I put in a new thermostat.

So the combination of a busted thermostat (probably stuck open) and cold weather made the engine too cold and that led to all the sensor shut offs. Now the gauge reads right in the middle, where it is supposed to.

I had to update this so people looking for the answer knew.

 

[That210Guy]

Where did you get a new thermostat at?

 

[Spad]

Where did you get a new thermostat at?

Not sure where the OP got his, but I suggest going with the ACDelco OEM part 15-11073. Ebay is a good place to find them under 30 bucks.

 

[That210Guy]

Not sure where the OP got his, but I suggest going with the ACDelco OEM part 15-11073. Ebay is a good place to find them under 30 bucks.

Awesome, thanks man.

 

[Bobby Boucher]

Not sure where the OP got his, but I suggest going with the ACDelco OEM part 15-11073. Ebay is a good place to find them under 30 bucks.

Sorry, haven't been on in a while. I got mine from O'Reilly's, don't remember how much it cost.