Hello. New here. Looking for any help I can get on this one - I'm stumped. Started getting ENGINE HOT/AC OFF error message on my '06 SS w the 5.3l 8cyl. Car continues to run fine, but once the ignition is turned off, the car will not start again until I disconnect the battery to reset the computer. Also, as soon as the message appears, the temp gauge falls to no reading. Temp is NOT hot when this message comes up, sometimes it pops up as soon as I start the car cold.
I had engine diagnostic done on the car after the message appeared - code came up as Coolant Temp Sensor. I replaced the CTS, same thing continues to happen. Local mechanic seems to think there should be 2 such sensors, ont to feed the computer and the other to feed the cluster gauge, but could not find a second sensor. I checked the Haynes repair manual and there was no mention of a second CTS for the 5.3.
This is happening about once a day now, and Im getting frustrated... Coolant is clean and full. Even tried replacing the CTS a second time in case first one was faulty - same thing. Im able to find very little info on this, as it seems there isn't a whole lot available on the 5.3s.
Anyone out there have any knowledge or experience with this one, insight, suggestions, etc? I'd love some help. Thanks!

 

Did you get your car tuned?

 

No, nothing like that. All original.

 

Check your fans, the problem lies with your fans in your engine. They may be not spinning at how they should be, or spinning too fast. I cant see them spiiing too fast causing a shock within the electric system, so they may not be spinning well enough. Check your fuses and your fans and then let me know what you find.

 

Thanks. I will check the fans and the fuses. I know the fans DO kick on when the ENGINE HOT/AC OFF light kicks on, and they seem to run pretty fast. But if they weren't running right, wouldn't the temp gauge show hot before the error message displayed?

 

Not really. Your temp gauge could show that the internal temp of the engine is still cool, but something is giving off a reading stating that its still hot. Or something is hot, I remember when my car gave off that error, it was due to the polarity of the fans, not producing the electric circut that they should. Only due to a tune though, so, it may be different for you, but I would check with the fans first.

 

Check the thermostat? I had the same warning, it was the t-stat stuck open that triggered a coolant warning. See my thread about the same warning


https://montecarloforum.com/forum/en...-sensor-40462/

 

He's hit the nail on the head! I had the exact same problem/ message on my 3.5L years ago and it was the Thermostat stuck open. My guess would be, you change your thermostat and your problems will go away.

 

Thanks so much everyone. I will def put a new thermostat on there and I'll let you all know!

 

Did that ever work? Currently have a 2006 monte carlo ss 3.5 6cyl (I honestly don't know, but I'm almost sure that's right). Currently have been having a lot of issues, but this has been a recurring one for me throughout the years of owning the Monte. It really only seems to be in the winter time, but this notification comes up, the temperature gauge goes down to 0, and the heat only works if I give it gas. Sometimes it will stop mid-drive and the temperature gauge goes back to normal, heat works fine, etc. And sometimes the whole drive is fine. Just want to know if this fixed your issue, even though this was a long time ago.