I drove it last night and watch the DIC, it got up to 192 and stayed around there. I'll keep watching that. "Ghosted" was an auto-correct error, I meant "Hoisted up." They hoisted it up at the shop, and the error code popped up after... But I think it's just a coincidence that the CEL appeared right after the shop have it back, because the fan was acting up before that. I'm waiting for the code to pop up again and will post it. How many miles does it take for the codes to pop back up, 50? I was gonna check the scan tool LIVE data again to see if the temperature is acting goofy on there. ​​​​​​I tapped on the fan relay inside the engine fuse box, #50 I think it was, but that didn't turn the fan off.

Thermostat, temp sensor, or control module? What's it sounding like? No ac too.

 

Burp the cooling system https://www.chevyhhr.net/forums/how-...-system-60614/

Make sure the coolant is full. Have the codes read again. No sense in making wild guesses about what the problem is.

 

I have no clue. Maybe a sticky relay. All of the codes that I can guess at with the partial relate to the gas pedal/throttle position.
Don't clear codes, most will stay in memory to be retrieved later. Only "current" codes are relevant to the CEL. Don't get excited about "stored" or "history" or "permanent". Fix the fault=light goes out. Then after 50-100 cold starts everything gets forgotten (unless it is an EPA code).

 

 

Yes PCM troubles,

https://www.obd-codes.com/p0606

 

• There's a heat wave in MN right now while this is happening, daily highs in the low/mid 90°s

• The radiator fan stays on after the vehicle is turned off, even when the DIC coolant temp is lower than 200°, which matched the "live data" on this scan tool. The fan turns off after 5-10 mins.

• I read that's it's common for this code to disappear on it's own, but I expect that means it'll continue to reappear. It has disappeared on it's own now.

• While reading up on this issue (P0606), I've seen it's recommended to check the wiring to the PCM for frays and shorts, and that's a common type of issue that sets this code. Anybody know any good information for doing that?
• In case this helps, I took pics of live data
• 
  is it normal for the STFT B1 to vary - to + seemingly erratically?
  
  
  
  
  
  
  

 

You can check the wires , your eyes are your best friend. But, the code means internal fault/processor performance. I.E.: dead computer.
Check on ebay there used to be a couple of vendors selling used ECMs programmed to your VIN for around $120. You do need to have the crankshaft relearned.
Once you get the new one it is just plug n' play, then you will probably get a code for no crankshaft data. Shops with a computer like a Tech2 can do it.

There is a place on ebay that will program a ECM that you provide for around $50. Worth investigating.

Scroll down to the bottom of this page for a list of sites that can do it.
https://www.ebay.com/sch/i.html?_fro...op=15&_udhi=75

 

The extremely hot weather plus the overheat condition took the ECM to temperatures it probably never saw before. High temperatures can cause hiccups in solid state electronics. It seems worth a try to clear the codes and see if anything comes back.

Also, it is imperative to monitor the coolant temp and level very closely for awhile, as well the oil level, and check for signs of coolant in the oil and vice-versa. Maybe even do an oil change soon and have the oil tested. There’s a chance of warpage resulting in head gasket problems.

 

Anybody notice ECU voltage is 12.2 volts?
dead battery , a dead battery!

 

X2 on what Oldblue stated.
ECU volts at 12.264 is a dead battery.