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2008 gmc envoy_slt
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Discussion Starter #1 (Edited)
***UPDATE IN BELOW POST******

the truck is a 2008 ENVOY

So my mother took her car and got in oil change. soon after she realized that her A/c would sometimes cut out. at the same time her temp gauge and only her temp gauge, stops working. the needle doesnt move the few times i drove it but she said htat sometmes it does work, i dont know. i also thought a low wiperfluid light was on but she said that she thinks its the temp gauge (looks kinda like a windshield with a wiper). that comes on almost instantly after starting the car.

i did notice a weird sound that sounds like a ****ty muffler when she starts her car but it does away after driving a little but. this isnt my car, so i cant really say what is and what is normal, but i know that sound when she starts the car is NOT normal. its sounds like a bad muffler but i dont think it is coming from the muffler. again she just took like 2 weeks ago to get the oil changed, dont ask why she didnt take it right back to them.

but any ideas on what might be the problem? or if it it multiple things? could it be just somehow disconnected wire when changing the oil? but why is it only the temp gauge?

any help is appreciated

thanks
 

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2004 gmc envoy_slt
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2,415 Posts
Someone may have damaged the external temperature sensor or disconnected its connector while the oil change was done. The temp sensor is mounted on the radiator support about in the center. This will affect the AC as well because it uses the ext. temp to adjust the interior AC temp.

For the engine noise, you will need to look and listen around the truck to isolate it. Mufflers shouldn't fail this early, unless it was damaged by road debris.
 

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2008 gmc envoy_slt
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Discussion Starter #3
Ok heres an update

I took the car to autozone so they could run the codes. and this is what came up

the code P0128

and told me to check t

1. the coolant level- that was ok

2. thermostat defective

3. ECT (engine coolant sensor)

whats weird is that the gauge worked today along with the AC. the whole time I took it in.

the sound when you start the car is still here but I don't know if its related yet. also after driving and I park it and turn the engine off. when I go to start it, it starts slow. like the battery is a little dead. but it starts after a little delay.
 

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2008 chevy trailblazer_lt
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2 Posts
Have you resolved the problem? I'm literally having the same issue. Ac is out and the temp gauge is flatlined. Desperate for aNY ideas
 

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2003 chevy trailblazer_ls
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5 Posts
Any updates on this issue? Im a new member and dont want to start a new thread since it seems to be a common issue. My gauge is pegged all the way down at 100 and and AC will only work for about 5 min when truck is cold. Truck has new ect sensor and tthat.
 

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2003 chevy trailblazer_ls
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Any updates on this issue? Im a new member and dont want to start a new thread since it seems to be a common issue. My gauge is pegged all the way down at 100 and and AC will only work for about 5 min when truck is cold. Truck has new ect sensor and tthat.
Ok, here is where I am so far with my issue. All totally irrelevant issues. My themp gauge does not work at all. My AC was going out due to the airgap being too large between the coil and the pulley so it would disengage whenever the temp on the compressor would rise. A simple adjustment fixed the issue AC and now it blows all the time. My next task is the temp gauge which might be a bad stepper motor. I'll be tackling this task soon.
 

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2008 chevy trailblazer_lt
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14 Posts
OK I have the same problem, When temp guage does not work, the A/C will not work, After driving a while the guage will start working and the A/C at the same time. If I disconnect the battery and reconnect all works fine for a couple of trips. Has anyone found a real fix for this, The ect sensor is hid pretty well. I took a pic of what I think is the connector, will try to attch, Can anyone verify that is it? 2008 trailblazer LS, 4.2 engine
 

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2002 chevy trailblazer_ltz
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2002 TB A/C issue

My A/C works fine, until the ambient temp goes above 76-degrees, then is blows hot air.

The system is full, as per spec.

Anyone have an idea what's wrong?

Thanks.
 

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2008 chevy trailblazer_lt
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14 Posts
ect sensor

OK had the sensor replaced , the guy at the oil change place replaced it for me, He said it was behind the alternator, not on the passenger side. this is a 2008 trailblazer LS 4.2 engine. This morning, same problem, Gauge works for a while then fell to 100 and no A/C. Does any one have a good fix for this, or maybe a wiring diagram?
thanks
Charlie
 

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2008 chevy trailblazer_lt
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4 Posts
2008 TB with six. Same exact problem. It's an intermittent problem. AC is fine when it's running and the temp gauge is reading correctly. Seems like a chronic problem with this model. Any fix yet?
 

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2008 chevy trailblazer_lt
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2008 tb

I too just started having this problem. I actually just bought the truck. Gonna watch and hope for some more info. THX
 

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2008 chevy trailblazer_lt
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40 Posts
2008 Chevy trailblazer I-6 Engine: Intermittent Temp Gauge / A/c

Hello,

My 2008 Trailblazer has been throwing the PO128 OBDII Code on and off for the past 4 years. The intermittent engine coolant temperature gauge & A/C always fail to work at the same time. 98% of the time, the issue usually appears during the Fall, Winter, and Spring (the cooler months), when the nighttime temps drop below 70 degrees. The other 2% of the time that the issue occurs is during the summer time whenever the nighttime temperatures drop by 20 degrees or more from the previous day's high temperature.

I just took a look at the location of the two-wire Engine Coolant Temperature Sensor's (ECTS) location on my engine. It is buried near the engine's #6 cylinder, and is located in the cylinder head. Not an easily accessed location.

The intermittent failure seems to tell me that the ECTS "Should" not be the issue, as it has always been my experience that once an engine sensor fails, it's dead, and I have never seen one come back to life.

I just spoke with the local Chevy dealer's Service Department, and they quoted me $390.00 + tax to replace the ECTS, flush the cooling system, and install new coolant. OUCH ! :bonk: Not only that, the Service Writer told me that changing the ECTS May Not cure the issue! He went on to say that the signal from the ECTS goes directly to the Engine Control Module (ECM) and no where else.

So, now I'm thinking that I will have to change the both the ECTS and thermostat, and hope that fixes the issue.

Does anyone know what the Flat-rate labor figures are for replacing the ECTS and thermostat on a 2008 Chevy Trailblazer with the I-6 engine? These two components are located as far apart as they can be on this year model of I-6. It was an obvious GM 'Great Mistake' (that was probably done intentionally) for them to move these formerly next-to-each-other components so far apart on the I-6 engine. That greed-generated design change occurred in the 2006 model year, I believe.

I am a 68 year old shade-tree-mechanic and not looking forward to the prospect of having to do the work myself, but being on a fixed-income, that will obviously be the case.

As far as tracing down the possibility of the issue having to do either with the wiring, the 'stepper motor' (whatever that is), the engine temperature gauge itself, or the ECM, I'm just a redneck in a rock and roll bar".

I would appreciate any thoughts on this issue...Thank You for your time.
 

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2002 olds bravada
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I just got a 02 Bravada AWD and the temp gauge is flat lines but it is too cold to test the AC operation. Also my speedometer occasionally works. I don't know if this is related to my inop AWD so I have some checking in order that is why I am looking here.
 

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2008 chevy trailblazer_lt
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4 Posts
Same problem with a 2008 TB ST. Intermittent loss of temp gauge and AC compressor. Appears completely random. Wiring harness connector?
 

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No fixes yet?

I'm having the same issue, mine seems to activate on certain bumps, and catching a speedbump just right will usually bring it back on. leading me to believe that it's a "wiring" issue. mine only started doing it in the last 6 months. I have seen other places where a couple of people claimed that replacing the ects and the thermostat fixed the problem.
 
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