[ChevroletCustomerService]

TxImpala, I know you're seeking advice from other owners but I just wanted to let you know that visiting your dealership would be a great next step. This way their specialized technicians can run the proper diagnostic checks on your vehicle. And if you would ever like assistance working with your dealership towards a resolution, please feel free to contact me anytime through private message on this forum.

Best,

Katie
Chevrolet Customer Service

 

[TxImpala89]

So on my way to work this morning the same message came on, this time with the "change oil soon & check engine light" managed to make it to where i change my oil regularly, they said the cam shaft sensor was leaking, I'm waiting here for further info

 

[TxImpala89]

Now they are saying intake gasket! They don't know anything! Taking my car to my mechanic

 

[Impala_Ken]

On my '06 Impala 3.5 I replaced the sensor and the problem went away for a few weeks but came back. The dash guage does not read directly off the temp-sensor, the sensor feeds to the computer and then the guage is fed by the computer (was told it is done this way because the temperature actually varies so much it freaks owners out). Once the computer senses an over-heat it puts out the "Engine Hot, A/C Off" message and for some reason drops the temp reading to "C". Changing the sensor probably restored the temp range to the computer and allowed me to run "error free" for a while, but my real problem was the thermostat. The little rubber seal at the valve portion had disintegrated (not the seal around the outside edge of the thermostat body). Have not had a problem since I replaced the thermostat.

Shortly after that I had another sensor go bad on a cold night, the engine oil-pressure sensor. I was working far from home, so I shut the engine down and coasted to a gas-station (thank God, it was below zero). The engine sounded okay, but did not want to chance it, so had it towed to the nearest Chevy dealer who determined my oil pressure was good and the sensor was bad. I have 215,000 miles and the car and engine still drive like it always had, so I cannot complain too much!

 

[Bobby69]

Try replacing thermostat first. I replaced my sensor first and still got the same code..

 

[retiredpauly]

Got the dreaded P0128 code today. Of course it's -18C and windy. Wife had car and pulled over and stopped as soon as it came on. ( bless her ) . I drove to where she was ( about 10 mins away) and determined that the engine was not hot and there was still fluid in it. The temp gauge was at the bottom. I recall reading something here a while back and thought it was this problem. I had her drive it home and searched here and arrived at this thread.
I also did a you tube search and found this video.

Went to the garage and in about 15 mins I had the thermostat out and it looked exactly like the one in the video.

I ordered one from my parts guys and ordered a spare seal as well. There is mention of it being a bit of a PITA to reinstall. While I was waiting for the parts to come in ( about 4 hours ) i messed with the old one re-installing in and out of the thermostat housing. I found that a coat of Sil Gyde was the trick. I took the spare seal anyway as I ordered it.
I also had a chance to use my Air Lift that I purchased a while ago. The very same tool as mentioned in the video.
It works AWESOME !.
But
It refills so fast that you have to keep an eye on whatever your sucking the antifreeze from as it's empty before you know it.

Took me about 20 mins to reinstall the thermostat and another 30 minutes with the air lift. Now that I have used it will be faster next time.
System held 25 inches of vacuum for 15 minutes so no leaks.

Started and ran it for 10 mins and no leaks. Waited till i could feel a little heat in the upper hose. Both AC fans still running at this time as code was still present.
Shut it off, cleared the code and the temp gauge jumped right away.

Re start and test run on highway and all is well.

Guess this could be a GMG/FMB/DIY/TOOL BOX/P&T 8th Gen posting.

I will write up in tool box about Air Lift.

 

[463]

new temp sender :idea:

 

[retiredpauly]

Nope
You can clearly see the thermostat is pooched.

 

[463]

new temp sender :idea: . That will be the next thing you put in.

 

[retiredpauly]

Perhaps.

Most on here that I read that had this error changed the sensor and the warning came back on.
Not saying it won't fail but the defective thermostat seems a good bet so far.

 

[463]

With the temp gauge on cold and the "Hot Engine, A/C Off" message is on and coolant recovery tank at normal means the sensor is at a point of fail.
If the T stat had stuck closed the car would have boiled over and the temp gauge would been on hot.
When temp is on cold and the "Hot Engine, A/C Off" message is on is the main clue for the sensor that is failing.
This sensor will recover to normal and will repeat again in the future.
Keep us posted.

 

[retiredpauly]

The gauge was not necessarily on cold but appears to have been in the "off" position.
Normally when you put the key to the run position the gauge will lift a bit off the bottom.
With this message on, the gauge was sitting in the "key off" parked position.
I will keep an eye on it and advise.

 

[463]

The way to check the thermostat is with a thermometer and a pan of water. As the temp rises to 195oF or it's temp rating, the thermostat should open smoothly and close when removed from the heat.
I have thermostats in a new car fail in the open in the dead of a winter storm and a new non gm thermostat fail in the closed and boil in the summer.:gaah:
So I will and have not installed a thermostat since without checking each and every one to make sure the they work as stated.

 

[retiredpauly]

Agreed.
The old stat has clearly failed in the partially open position.
The 97 Chrysler T&C minivan I did in the spring had failed in much the same way only the small pin at the top had become disengaged and was cocked sideways.
This new thermostat I bought was a Stant "Exact Stat" and although after market it was clearly more robust feeling in construction than the OE one.
Does not mean it's any better but an OE one was a day away to deliver in or a 90k round trip for me to get one.
If this one causes me trouble I will change it out as it's pretty easy to do.
I do normally test them but in this case I took a chance and just put in.
Drove the car again today at -20C cold start and it worked just fine.

 

[paw5300]

xFantasyFiendx,

Looks like SystemCheck2006 was able to find a fix. If there’s anything that Customer Service can help with (looking into warranty/recall information, dealership interactions, etc), I’m available.

Best,
Sarah
GM Customer Service

im having this same exact problem. i have changed the thermostat and temp sensor. the problem is still there. any suggestions???

 

[retiredpauly]

Did you clear the code ?

How long did you run the car?
Get all the air out ?

 

[r.mosley]

11-04-09

"Engine Hot A/C Off", No Engine Light, Temp Guage reads dead Cold. Cooling Fans are running full boar after engine start and car is cold. This happened after I was on my way to work (6 miles on the freeway). All was good, then BAM! the message comes up and guage reads dead cold (and the engine is hot after driving for 10 mins).

I pulled connector off coolant temp sensor and connected to a new one I picked up at Advance Auto ( but not installed in block) just to see if original unit was not reading. Hard to get a volt meter to the pins on the installed sensor to ohm it out. The engine hesitates to start for a brief moment and after start with new sensor connected and "Engine Hot A/C Off" still shows up with guage reading Cold. Not sure if battery has to be disconnected to reset ECU or if not necessary since there is no check engine light.

I connected connector back to sensor in the block and restarted. Engine again hesitates the first time starting briefly and "Engine Hot A/C" comes up again and coolant temp reads Cold. Note: after the 1st start when connecting new sensor and 1st start with original sensor, hesitates briefly to start... any other start after that starts up fine as long as I don't switch sensors (hope that made sense).

I forgot to mention that I did get my oil changed the day before at the dealership and had my tires rotated. They have to perform a transducer cal for each wheel when they are rotated since they the car has the "Tire Pressure Monitor System". I called them to see if this may have been a result of they "calibration" possibly and they replied that the message could be from a multiple of reasons and it would cost me $95 just to take a peak (Diagnostic Fee... that's funny)

Any help is very appreciated


UPDATE! 11-05-09

I was driving home after work yesterday and my check engine light did come on. So when I got home I just disconnected the battery for about 20 seconds and reconnected. Started the engine and the temp gauge went up to proper temp (so it's not the sensor, i assume) and no more ENGINE HOT A/C OFF message.

Then this morning going to work the message came up again about the same point as it did yesterday (axp 6 miles on freeway) morning and check engine light came on in the afternoon on my way home as did yesterday (my trip to work is about 10 miles mostly freeway).

UPDATE! 11-06-09

I reset the battery again this morning before going to work. All was good again and now it's back on... same thing after 6 miles, like clockwork. I will verify tonight if check engine light comes on again. Any tips

It's the thermostat.... Same thing happened to my impala. It's not warming up fast enough for the computer to realize it's at operating temperature.