Hot Engine Air Conditioning Off
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Race Director
Joined: May 2012
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From: Phoenix area, AZ
Hot Engine Air Conditioning Off
On my way to work this morning I got the "Hot Engine Air Conditioning Off" message on the DIC. I looked down and saw that my HUD was showing the engine temp maxed out, and the dash gauge had completely stopped working. I stopped at a gas station on the way and checked the fans, etc. to make sure they were all working since I've had recent issues, but everything was operating normally so I continued on to work with no mishaps. Aside from the temperature sensor is there anything else that could possibly cause this to happen? If it's the temp sensor, it will be covered under warranty by the shop that did my recent work, but if it's something else I'll have to track that down myself. TIA.
Melting Slicks
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From: Mead Wash
2020 C6 of the Year Finalist - Modified
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Easily solved Ed. Don’t go to work anymore. Seriously, more then likely temp sensor or wire fell off of sensor.
Safety Car
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Thread Starter
Race Director
Joined: May 2012
Posts: 15,762
Likes: 3,281
From: Phoenix area, AZ
Thread Starter
Race Director
Joined: May 2012
Posts: 15,762
Likes: 3,281
From: Phoenix area, AZ
So from the research I've done I'm planning on hooking up my OBD reader after work to see if there are any codes, and if so I'll clear them to see if that fixes the issue. If that doesn't work, I'll try disconnecting the battery for 10 minutes.
Race Director
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What work was done to the car, since if they opened up the radiator collect system, best guess is air in the lines that was not vacumn pulled out, and air bubble got trapped at the sensor.
Hence if wire temp sensor fell off, or engine temp sensor going south, then temp reading should have dropped (held constant if it was going out), not have the engine temp go to max instead. But, when you get a air bubble trapped at the sensor, then that part of the engine will heat up, and this causes the false temp sensor reading instead.
As for disconnecting the battery, will do nothing with the History DTC codes that are stored, and will either need enough run cycles to cycle them out of history if problem does not reappear to trip another code into history,may need to get something like a Tech II on the car to clear the body level codes isntead. Hence standard basic code reader only does the upper codes, but will not reach down into the EBCM or BCM body level type codes to read or clear them instead. Also, as problem clears itself since the BCM does a check of the modules every start up, DTC will no longer show codes, but they are still stored in the History until either start cycled or tool erased instead.
Short of that, then start checking the engine temp sensor wires, since the sensor if just a stat that works off ohm readings that the lower the engine temp, the lower the ohms through it/the higher the gauge will read. so if they pinched/ grounded out the temp sensor wire, will cause the sensor readings to max out as well.
Hence if wire temp sensor fell off, or engine temp sensor going south, then temp reading should have dropped (held constant if it was going out), not have the engine temp go to max instead. But, when you get a air bubble trapped at the sensor, then that part of the engine will heat up, and this causes the false temp sensor reading instead.
As for disconnecting the battery, will do nothing with the History DTC codes that are stored, and will either need enough run cycles to cycle them out of history if problem does not reappear to trip another code into history,may need to get something like a Tech II on the car to clear the body level codes isntead. Hence standard basic code reader only does the upper codes, but will not reach down into the EBCM or BCM body level type codes to read or clear them instead. Also, as problem clears itself since the BCM does a check of the modules every start up, DTC will no longer show codes, but they are still stored in the History until either start cycled or tool erased instead.
Short of that, then start checking the engine temp sensor wires, since the sensor if just a stat that works off ohm readings that the lower the engine temp, the lower the ohms through it/the higher the gauge will read. so if they pinched/ grounded out the temp sensor wire, will cause the sensor readings to max out as well.
Last edited by Dano523; Dec 12, 2021 at 01:42 PM.
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Thread Starter
Race Director
Joined: May 2012
Posts: 15,762
Likes: 3,281
From: Phoenix area, AZ
What work was done to the car, since if they opened up the radiator collect system, best guess is air in the lines that was not vacumn pulled out, and air bubble got trapped at the sensor.
Hence if wire temp sensor fell off, or engine temp sensor going south, then temp reading should have dropped (held constant if it was going out), not have the engine temp go to max instead. But, when you get a air bubble trapped at the sensor, then that part of the engine will heat up, and this causes the false temp sensor reading instead.
As for disconnecting the battery, will do nothing with the History DTC codes that are stored, and will either need enough run cycles to cycle them out of history if problem does not reappear to trip another code into history,may need to get something like a Tech II on the car to clear the body level codes isntead. Hence standard basic code reader only does the upper codes, but will not reach down into the EBCM or BCM body level type codes to read or clear them instead. Also, as problem clears itself since the BCM does a check of the modules every start up, DTC will no longer show codes, but they are still stored in the History until either start cycled or tool erased instead.
Short of that, then start checking the engine temp sensor wires, since the sensor if just a stat that works off ohm readings that the lower the engine temp, the lower the ohms through it/the higher the gauge will read. so if they pinched/ grounded out the temp sensor wire, will cause the sensor readings to max out as well.
Hence if wire temp sensor fell off, or engine temp sensor going south, then temp reading should have dropped (held constant if it was going out), not have the engine temp go to max instead. But, when you get a air bubble trapped at the sensor, then that part of the engine will heat up, and this causes the false temp sensor reading instead.
As for disconnecting the battery, will do nothing with the History DTC codes that are stored, and will either need enough run cycles to cycle them out of history if problem does not reappear to trip another code into history,may need to get something like a Tech II on the car to clear the body level codes isntead. Hence standard basic code reader only does the upper codes, but will not reach down into the EBCM or BCM body level type codes to read or clear them instead. Also, as problem clears itself since the BCM does a check of the modules every start up, DTC will no longer show codes, but they are still stored in the History until either start cycled or tool erased instead.
Short of that, then start checking the engine temp sensor wires, since the sensor if just a stat that works off ohm readings that the lower the engine temp, the lower the ohms through it/the higher the gauge will read. so if they pinched/ grounded out the temp sensor wire, will cause the sensor readings to max out as well.
Thread Starter
Race Director
Joined: May 2012
Posts: 15,762
Likes: 3,281
From: Phoenix area, AZ
Update on this issue.
Not long after I last posted the temp sensor finally triggered a code, and the check engine light came on. I'd planned on clearing it out once I got home, but the sensor started working again and the ECM cleared it out on its own. Now about a month later I haven't had a single reoccurrence of the issue. Hopefully that's the end of it. Hope this helps someone in the future.
Not long after I last posted the temp sensor finally triggered a code, and the check engine light came on. I'd planned on clearing it out once I got home, but the sensor started working again and the ECM cleared it out on its own. Now about a month later I haven't had a single reoccurrence of the issue. Hopefully that's the end of it. Hope this helps someone in the future.
Race Director
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From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
I had an intermittent wiring issue in the infamous fan wiring connector. As it turned out, that every time I did a continuity check, the movement of the wiring was enough to re-establish the connection. I lost a few hairs on that one, but the timing worked out, since a good deal on a C7 appeared before I found the root cause.
