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2003 chevy trailblazer_lt_ext
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Discussion Starter · #1 ·
So I read through all the threads here just to keep up to par on my '03, and one thing keeps coming back to me, most everyone states the temp gage should be at 210F or a little higher, a couple ticks below the 210 mark could means thermostat problems.........so since day one my gage has read 3 ticks below 210 after the engine reaches normal operating temp, everything seems fine, no codes, and in the winter, the heat comes out warm soon after starting out, that leaves me to think all is well with the thermostat. If the thermostat is opening prematurely or is stuck open, exactly how would that effect the performance of the engine, would it have an effect on fuel consumption, and would the pcm store codes without the check engine light coming on. one last question, if it were 70f outside and you started your truck and just let it idle, how long on average would it take for the fan clutch to engage?, I am just trying to understand the whole cooling system to give me piece of mind that it is functioning properly with the warm season coming :thx
 

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2002 chevy trailblazer_ls
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Could be the instrument panel temp gauge is out of calibration. I would use an OBD 2 reader that will display the coolant temperature and see what value it's actually sending to the pcm. That would tell you if the cooling system is running low temp or if the gauge itself is off by three "ticks". At full operating temp mine typically stabilizes around 205°F.
 

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2005 chevy trailblazer_ls_ext
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:iagree:

What he said! :D

Actually we had someone else talk about this not very long ago. Might want to search through the threads.
 

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2003 chevy trailblazer_ls
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I agree with him.
try to read the temp from the OBD port.
From my OBD port- I see 215 degrees.
 

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2005 chevy trailblazer_ls
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Not so much that the temp is a bit below 210 on the thermostat question, but the temp gauge moving around a bit is a pretty good indicator the stat is on its way out. Mine would get up about 1/2 way to 210, go on up when I started driving, and drop/rise from there. Changed the stat, and it's dead on 210 now all the time. My scanner won't display the actual temp output unless there is a code, so I don't know what it is really running, but I feel pretty good about it unless it moves again.

Sounds like calibration since it's always done it. Other than that, I would think the ECT sensor may be giving faulty info. Probably not, they don't tend to go out very often from what I've seen on here.
 

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2002 gmc envoy_slt
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My original stat was nearly 3 bars below the 210 mark and didn't set a code, and I verified the engine was staying below the 192 degree rating of the stat by connecting my scan-tool. Even hovering between 179-184 degrees, the PCM hadn't set a code, so I don't know just how 'cool' you need to be in order to have a code set. With the new stat, the needle is just about at 210 (verified at 208-209 with my scan-tool) and gas mileage is back up. Keep in mind I have e-fans, so my needle actually goes to the line past 210, just as the fans kick on to cool it back down.

Our temp gages are NOT 100% accurate, nearly 3 lines past 210 is registers at around 218-219 and 2-3 bars below is the mid-180s, so while 210 is nearly spot on, the other's aren't proportional.
 

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Western Canada Chapter
2003
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My original stat was nearly 3 bars below the 210 mark and didn't set a code, and I verified the engine was staying below the 192 degree rating of the stat by connecting my scan-tool. Even hovering between 179-184 degrees, the PCM hadn't set a code, so I don't know just how 'cool' you need to be in order to have a code set. With the new stat, the needle is just about at 210 (verified at 208-209 with my scan-tool) and gas mileage is back up. Keep in mind I have e-fans, so my needle actually goes to the line past 210, just as the fans kick on to cool it back down.

Our temp gages are NOT 100% accurate, nearly 3 lines past 210 is registers at around 218-219 and 2-3 bars below is the mid-180s, so while 210 is nearly spot on, the other's aren't proportional.
I have to re-iterate the point that the t-stat can sit a little below normal, not throw a code, and kill your mileage in the process. I changed mine after watching it sit low for almost a year. It finally threw the code when the conditions were right but the money I wasted on fuel waiting for the code just rots my balls :duh::bonk: As ylab indicates in his post...... The mileage will climb back to respectable numbers once you get it back up to the 210 range. The truck is set up to be there and anything lower starts to cause you to run in cold mode and you run excessively rich. The PCM allows it as it thinks the engine is cold.

The gauge is not accurate but a low reading means it is saying it is below normal. Change that T-stat now and save some money in fuel :thumbsup:
 

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Operating temperature ?

Hi !!

What should be the REAL Operating temperature my OBD II scanner should show me from GM's preset ??

I've seen 210 in dash BUT is it the same from the scanner tool ?

:thx
 

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Ok !! Now I have my new scanner and first test gave me 199-201 F. So it should be fine I guess ?

:undecided:thx
 

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2005 chevy trailblazer_lt
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If your fuel mileage is ok then there may be another possibility. If the steppor
motors have been replaced then the needle on the temperature gauge may have been reinstalled in the wrong position.
 

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Mistral150--On my 2003 Envoy, both the scanner and guage read a steady 200F degrees after warm up and track each other from a cold start to warm up.

C.B.
 

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The point here is that I get 10-11 MPGs so I was woundering if that would be enough too rise my MPG, because I read everywhere that I should get 210 instead of my 200. So would 10 degrees make that huge difference in my MPGs. ???

:grouphug::thx
 

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I don't believe so. I get 17-18 around town with some distance mixed in and 22-24 when all Interstate. You've got other problems than a bad thermostat.

C.B.
 

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My gauge says 200 but my OBD2 scanner reads 185 degrees when fully warm. I am still trying to work out a P0303 (cylinder #3 misfire) code...could this be related in any way?
 

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2004 gmc
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No. The number on the gauge is a lie meant to reassure Ma and Pa Kettle that everything under the hood is stable and drama-free, even if you're coasting down or climbing up a 6000 foot mountain.

The gauge will appear to be locked at 210 whether the raw data from the scan tool reads 180-225 typically.

The oil pressure gauge in the I6 is an even BIGGER lie, since the sensor is a 12 PSI on/off switch! They just fiddle the needle a little bit according to RPM and temp, because nobody would believe a rock steady oil pressure needle. The temp gauge, on the other hand, the Kettles EXPECT it to not move, which is nuts and we know better.
 

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My temp. gauge was reading 2-3 lines below the 210 mark a couple of weeks ago so I changed the t-stat. After the t-stat was changed the gauge was within a needles width below the 210 mark for 2 weeks. Everything seemed just fine. I never got any CEL before or after so i couldn't check the codes. This morning I was driving for 45 mins and the guage was 2 lines below 210 again. Driving home tonight the guage was 1 line below 210. I don't have a scan gauge so I can't check anything. Could it be the coolant sensor? I'm really close to buying one from Rockauto and trying it. Any thoughts?
 

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Bad thermostat or sensor. Much less likely to be the stepper motor on the gauge. A scan tool could confirm the last idea, but can't distinguish between the first two.
 

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Premium Member
2003 chevy trailblazer_lt_ext
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Discussion Starter · #20 ·
Think about this one....replaced thermostat a couple years ago due to code, in the meantime I picked up a scanguage 11 and monitor the water temp, as well as trip mpg.... the other day I had taken an 85 mile trip to pa during a warm day with the a/c on and scanguage reporting temp of 175-180f and my trip mileage was 20.5mpg average............the trip home at night was without the a/c on and the scanguage was reporting temps in the range of 159-177 without throwing any codes but get this, the average mpg reported for the trip back was 24.5mpg,I would think with the lower temps the mileage would be crapola but it was just the opposite.......I did just replace the plugs a couple days prior but I dont know if that could influence the running temp, I am starting to think my temp sensor must be malfunctioning......any ideas?
 
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