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My coolant temperature gauge(digital) intermittently goes blank showing only three dashes instead of the temp. When it does this my air/heat will not work. Any idea what this isM
 

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Classic sign of bad thermostat. Car takes too long to come to operating temp.

ECM shuts down A/C.
 
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Discussion Starter · #5 ·
Thanks for the info! I had the engine coolant sensor replaced yesterday, only to have it go back to the same thing this am. I will see if the mechanic comes up with the same answers as you guys (who i'm sure know way more) :)
 

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I had the triple dashes also recently but intermittently. Sometimes even on and off during the same drive.

My logic says triple dashes is NOT a thermostat issue. If the sensor is sending a signal to the ECM you would have a value on the DIC. Maybe it's 60 degrees because that's the current temperature. As you drive, the temperature would rise, but very slowly if the thermostat is stuck open. This would give you a code for not coming up to temperature in the allotted time.

If the T-stat was stuck closed, your temperature would rise rapidly and the car would overheat, BUT you would have a value on the DIC.

If there is NO signal being received it would seem the DIC reads the triple dashes and the ECM turns the cooling fan on high and disables the A/C to preserve the engine - assuming worst case that it's too hot because it doesn't really see what temperature it truly is.

Last weekend I had the triple dashes again, then a value, then we stopped for lunch. Had triple dashes when we left and a CEL by the time we arrived home. Read the code and it was the "too long to heat up" (forgot the actual code) message. Cleared the code and started it back up, temp read 175-ish.

I just went out and disconnected and re-connected the cable several times, started it up, and had a reading. Will monitor it over the next few runs to see if it stays off.
 

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Classic sign of bad thermostat. Car takes too long to come to operating temp.

ECM shuts down A/C.
This is my understanding as well. The car takes too long, or doesn't make it to operating temp and the ECM throws '---'. But I've never had it happen as mine actually would get stuck closed and not open and my car would see 225.... I knew that day it was time to replace it.
 
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Thermostats can get stuck open, closed, or any point in between. My RL currently has it's stuck about half open, so it warms too slowly and won't always reach operating temperature on a cool day, but does OK on a warm one. It is parked for now, and is getting a new thermostat as soon as I have a free weekend.
 
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Had this happen to me and it was the thermostat replace it just make sure you get a quality piece . Read my August 2015 thread on this subject to give you some insight .
 

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Again - high readings = stuck closed. Slowly increasing readings = stuck open. No reading = no signal from sensor.
 

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I think that @The_Ghost is correct, that the --- can mean that the engine is warming too slowly.
Then why would I see it immediately upon starting the car on one key cycle and not the next? Why would it be there when I start driving, then get a value during the drive, then have it go back to the dashes later (after reaching normal temps)?
 

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Sounds like you may have a faulty coolant temp sensor .When my car overheated my DIC showed a temp of 203 I let it cool down refilled and burped the system then got --- on my DIC display . When I got home I was at the Dream Cruise at the time talked to a friend who was familiar with the Ecotec engine and he said this was a common problem with a 2.4 .I took his advice and replaced the sensor , thermostat and coolant and have not had a problem since .
 

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Sounds like you may have a faulty coolant temp sensor .When my car overheated my DIC showed a temp of 203 I let it cool down refilled and burped the system then got --- on my DIC display . When I got home I was at the Dream Cruise at the time talked to a friend who was familiar with the Ecotec engine and he said this was a common problem with a 2.4 .I took his advice and replaced the sensor , thermostat and coolant and have not had a problem since .
That was my thought also - either a corroded connection or the sensor is on it's way out. I was hoping to prove it out with a few drives this weekend but we're towing the trailer to a nearby state campground. MTF
 

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Then why would I see it immediately upon starting the car on one key cycle and not the next? Why would it be there when I start driving, then get a value during the drive, then have it go back to the dashes later (after reaching normal temps)?
I did say "can" and not "does". but to avoid misunderstanding my post should have said: "I think that The_Ghost is correct, that the --- can also mean that the engine is warming too slowly"

Many symptoms can have more than one solution, and there have been several threads that discussed this issue where it was solved by replacing the thermostat. It has of course alternately been solved by replacing the sensor, and by fixing wiring issues.
 

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Sometimes I tend to overdo things but when I changed my thermostat, I changed the sensor too. The coolant was drained, The thermostat was out, everything was out of the way, so I just changed them both. The --- disappeared for good. Still not sure which caused my problem but they are both relatively cheap parts and in my case throwing parts at the problem solved it.
 

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Drove to work Friday and coolant read consistently and accurately. Took it to town today and same thing. Appears in my case anyway, that simply re-seating the connector a few times cleaned it up.
 

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Drove to work Friday and coolant read consistently and accurately. Took it to town today and same thing. Appears in my case anyway, that simply re-seating the connector a few times cleaned it up.
I've been there and done that.
 

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Woohoo, my turn to get the dashes. Was working this morning (still showing around 90C), I drove out of town and then it started doing it.

Got back home, still showing dashes after restarting the car a few times, radiator fan seem to be running at full blast. No CELs yet. But I think at 73k kms it's about time, and I'm late for my coolant drain/fill.
 
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