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Discussion Starter #1
So I've been reading over the "Poor A/C at idle" thread on here and my problem is the exact same. About 45 degrees out of the dash when driving at 55+ mph, 60 degrees at 15-55mph and over 75 when stopped. I used one of those A/C dial temp gauges you stick in the dash to test.

That post says I need to update the fan clutch programming in order for it to spin faster at idle. That thread is 15 years old now however and I've read posts saying a new fan clutch would already have this programming on it. I wanted to ask to make sure though.

I have zero idea if the fan clutch has ever been switched out on this truck. Chevy says $142 to update the fan or $40 to check if it's already been patched. Apparently they can still do this even though that TSB is from 15 years ago which is cool.

Should I take it in to the stealership or just replace the fan clutch? I was thinking a new one could possibly work better but I know nothing about mechanical cooling fans only electric ones. The fan appears to work normally it will be at full power on cold start until drive the truck or rev the engine above 2500ish rpm for a few seconds. I think that means it works?

Any help would be appreciated. Thank you!
 

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Discussion Starter #2
Ok I pulled my Trailblazers VIN in the TIS system and it gave me this for history of calibration for my truck. This means for sure the truck already has this patch installed doesn't it? Especially the third one.

125963890000F846-New calibration to address customer complaint of overheat condition.
1258775300008AA7-Enhanced Calibration for Cooling Fan Noise Reduction
12583720000066CD-New calibration for improved fan control
1257635900004708-Enhanced EV Fan Calibration for Cooling Fan Noise Reduction and/or "Service Engine Soon" Light Illumination by trouble code P1484
1257547100004E62-New calibration to address complaints of fan noise
125734490000E14C-Calibration changes to fuel level curve and engine oil change telltale timer.
12572755000025C1-System calibration
 

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2002 chevy trailblazer_lt
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Have one of those cheap elm327 clone bluetooth obd adapter? You could monitor your A/C high pressure and you fan speed (actual and commanded) and see what is happening real time. I had an issue with mine where a previous owner had mangled some wiring and the A/C high pressure wasn't being reported to the PCM so the fan speed was not commanded higher when the A/C required it.
 

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Discussion Starter #4
I do have one of those adapters but what software can I use to see those? I didn't even see an option for those in ScanXL Pro
 

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2002 chevy trailblazer_lt
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The Torque app has some extended mode PIDs for GM. They need to be loaded after acquiring the app. The PIDs for the Fan and a handful of previously undocumented PIDs for the 4.2 can be found here...

 

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And of course any app that allows you to define additional custom pids should be able to use these pids. OBD Fusion comes to mind as one such app
 

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Discussion Starter #7
Turns out OBD Fusion does not allow custom PIDS, not at least for my '02. Says enhanced diagnostics not available. Followed your forum post and went searching for Torque, had no idea they didn't make an iOS version of it so I dug up an old android tablet of mine and got Torque Pro installed. I'll report back what the custom PIDs show. I'll take screenshots.
 

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So the OBD Fusion I have is android version. And I was able to load custom pids...

Screenshot_20191029-152312.png
 

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Discussion Starter #9 (Edited)
Ok, I tried manually creating the PIDs on a computer saving them to CSV and installing them and also manually typing them in on the Torque app and both have 0 results. Won't load anything. What am I doing wrong? Do you have a guide for creating the PIDs? I have a WiFi ELM327 tool that works with ScanXL just fine. Is my adapter incompatible?

Following a guide on a wiki this is how I formatted the CSV files. I made them in notepad and saved them as CSV

Engine Oil Temp,OILTMP,22115401,A-34,15,150,C,Auto
 

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Hard to say. I have never tried a wifi version but that seems unlikely to be an issue. Can you verify that standard pids for things like engine rpm and coolant temp work? That would confirm compatibility without having to delve into extended mode pids...
 

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2002 chevy trailblazer_lt
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Just rescanned through your posts. What year is your vehicle? You spoke of an update from 2005 and I assumed yours was an 05.
 

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Discussion Starter #14
Can you send the text contents of one of your PIDs so I can test it? You're saving them as .csv or typing them manually into the app? Strange your OBD Fusion allows for this and mine wont, I much prefer OBD Fusion.
 

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In android OBD fusion I selected settings, then 'User defined pids', then from the the top right menu I select 'New' for manual entry. Somewhere I have a csv for this also...
 

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This is the format of a csv export from Torque. This is from their built-in set of GM extended pids.


"[GM]Oil Temperature (Engine)","OilTemp","22115401","A-40",0,100,"°C","Auto","","",1
 

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Chevy Trailblazer 2008 LTZ (4.2L)
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Only the 2002 models had engine oil temp sensors.
I have 2008 and Torque shows the temperature of the engine oil. I know that it is not physically installed on my machine and that such sensors were only for 2002. However, this somehow works through the application.
 
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