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Author Topic: 07 Equniox 3.4L with "ENGINE HOT A/C OFF" on dash.. a few questions  (Read 9556 times)
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sorny
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« on: December 05, 2011, 08:58:33 AM »

Ok, my 07 Equinox suddenly started saying this on the dash and I noticed the temperature gauge isn't working at all.  It did this first thing on a cold morning so I knew it wasn't really overheating but that it must just not be receiving a temperature from a sensor and it's going into some kind of safe mode and running the fans at full blast and turning the AC off.  Well I went and bought a coolant temperature sensor yesterday.. there were 2 different ones listed for an 07 3.4L and maybe I just replaced the wrong one.  One was $15 and one was $23 and the guy at Advance Auto Parts (who usually don't know what they're doing, I know) says I need the $23 one.  I find that it's on the driver's side of the motor and it's pretty easy to swap so I do.  It looked like it may have been on the head but it could've been the block too (hard to see) from that angle.  I know it wasn't right on top of the hose neck that goes to the radio (and where I expect the thermostat to be).   I unhooked the battery so the ECM would reset the CEL on the dash and when I hooked it back up and restarted the gauge worked perfectly fine and no message about engine over heating.  I was glad it was just a $23 sensor.  Well then I drove for about 5 minutes and it did it again.  I watched the gauge just drop off from about half-way up down to zero and the ENGINE HOT A/C OFF comes back on the dash. 

Any tips?  Is there a second sensor?  Is it the one for the gauge on the dash?  Why would it work if I reset the ECM but then quit working a few minutes later?  Makes me think it could be an ECM problem because the sensor is dumb and should either work or not work and not be affected by the ECM resetting.

I appreciate any help.  The closest dealership is 45 minutes away and I'm not ready to pay them $100 or so just to diagnose this problem, let alone fix it.
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Terra-Nox
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« Reply #1 on: December 05, 2011, 09:08:57 AM »

Just a guess, but if you still have the CEL on I think Advance will scan for free.  From the symptoms it may have a P0128 code which 'could' be caused by a stuck open t-stat.
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2011 AWD V6  Terrain  Merlot/Titanium SLT2
sorny
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« Reply #2 on: December 05, 2011, 09:17:51 AM »

Good idea, I think they check them for free.  The light hasn't come back on yet (well, not sure, my wife drives the Equinox and I drive my Mustang).  But it was last time.  When googling around, which is how I found this site, I read that it could be a thermostat issue but I just wasn't sure why a thermostat being stuck open or closed would matter if it's a problem with the gauge.  If it was actually overheating and the gauge worked and showed that then I would definitely try thermostat first after checking coolant level, fans, and water pump.  I'm definitely not saying you're wrong, just talking it out and thinking about it.  Unless it was something like when the car gets to operating temperature and the tstat SHOULD open that's when the ecm goes crazy and just drops the sensor reading.  I don't know.  The Equinox has 80,000 miles on it and it probably wouldn't hurt to change the thermostat anyways as long as it's as easy to change as a regular, older, car.
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2012SLT-1
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« Reply #3 on: December 05, 2011, 05:19:13 PM »

Just a question here..  Did you happen to have your Block heater plugged in by chance?  My grandparents have an 07 Equinox, and there is a flaw with GM's Block heater that is installed.  When you plug your car in over night, if the engine temperature is above a certain temperature, it will throw a code at startup, because the coolant temp would be much colder etc.  There are many posts about this all over the internet.  I had the same problem with my 2006 Monte Carlo SS when I owned it.

Same DIC message you got.  After the next engine cycle the message went away.

Cheers
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2012 Terrain SLT-1 Fully Loaded Mocha Steel, AWD, V6
2013 Equinox 1LT Stripper V6, Summit White
sorny
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« Reply #4 on: December 05, 2011, 08:37:57 PM »

Nope, no block heater.  Don't even have one installed and it stays fairly mild here most of the time.  We get some cold days (near 0*) in winter but for example it was an unseasonably warm today and was around 64*.

What you mentioned would make sense if I was using a block heater except that wouldn't the gauge show the high temps?  My gauge stays on 0 all the time now.  For some odd reason if I reset the computer by pulling the battery cable then the gauge works again for a few minutes (with NO overheating warning) then after a few minutes the gauge drops from middle ways (normal range) to 0 and the engine hot message comes back on.  It's crazy.  I was sure it was the sensor, unless I replaced the wrong one.
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GM Customer Svc
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« Reply #5 on: December 07, 2011, 07:23:44 PM »

I would be happy to check and see if there is a second sensor. I will need the last eight of your VIN in order to do so. Please contact me privately for more assistance. Thank you.

Tricia, GM Customer Service.
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>>>>>> Please check out the new GM Owner Center at https://my.gm.com/ for more vehicle information!
sorny
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« Reply #6 on: December 12, 2011, 07:33:13 AM »

Just wanted to update you guys and let you know what I found out about the Equinox.  When I would reset the computer by unhooking the battery the gauge would work for a few (sometimes 5, sometimes 30) minutes before going back to 0 and the ENGINE HOT message coming back on the screen... but I noticed that before the message came up the needle never went more than 1/4 of the way up the dash.  And there was barely any heat blowing from the vents.  After I let the vehicle idle at a stop for a while it would rise up to about halfway and the heat would work again.  So I went and bought a thermostat and installed it yesterday--so far so good.  We drove probably 100 miles yesterday and it never came back up and the heat works great.  The needle stays around the middle area of the gauge and the heat works great.

So even though the engine wasn't actually running 'hot' I guess the computer is designed to have that same message come up when it realizes the car isn't warming up as fast as it should be.  Unless the car sat idle then you could drive it around all day (since it's been in the 20's and 30's lately) and it'd never totally warm up.  So anyways, $15 worth of thermostat and antifreeze took care of the problem.  Just wanted to update the thread in case someone else is searching for help on the same problem. 
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