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As it's in the title, since a week I have a crazy coolant temp gauge problem on my c6 Z06.
Was going to enjoy my beast last week-end, jump in, start it, let it warm up and suddenly the coolant temp needle start to went crazy. From zero to max temp and back to normal all in a couple of second with hot engine/ac turned off and check coolant message with fans at full throttle.
I was directly thinking about a bad coolant sensor as the engine was cold and all the levels were ok, but still disconnect the battery to see if it can help. Started again, problem still there, so I ordered a new sensor from ebay.
New sensor in place, started the car, everything was fine so I went for a quick test ride. 20 minutes without a problem and suddenly for just 1 second the needle raise the max temp and came back to normal.
Today I tried again, no problems and after 20/30min same sh*t.. And once it started to came back it was more and more often (every 2min) and finally was the same as with the old sensor.. and I even got the "change engine oil" message. Checked the oil life % and it was on 0 don't know why !! It's crazy
Tonight I start it again to see if playing with the wire or connector will do something, but without succes.. And the gauge was this time on 0 and stay there. Disconnected the coolant sensor and lost the little blue seal who fall somewhere in the engine bay, plus the connector touch the headers while I'm turning of the engine and it *****ng melted a bit !
So I'm totally lost now after 4 hours of research on google, find some peoples with the same problem but no one really fixed it. Did you guys have an idea ??
Hi EVRose, thanks for the quick reaction !! 3 or 4 years I suppose, I'm not sure.
It's funny that you mention the battery, because I was thinking to a possible low voltage making some trouble too as I haven't drive the car since almost 5 weeks.
I pull the battery out yesterday to charge it, will give a try today if I find that freakin blue rubber.
So, the battery was full, put it on the car and finally find my blue rubber seal and reconnect my temp coolant sensor connector !
Started the car, got the "hatch ajar" message, absoluty don't know what that means.. And again the "change engine oil" message..
Apart that, everything was normal until the coolant temp rise to around 70°C and then got again the "engine hot/AC off" message and this time the temp gauge falled to 0 and stayed there with screaming fans..!
To me, that's an electrical problem for sure. Plus the engine started after 3/4 seconds not immediatly like a bad ground or something.
I'm totally lost with that problem, what a sh*t
I also do a video, will post it on youtube and put the link below so you will see what happen. After more research on the net somebody got the same thing on a silverado if I'm not mistaken and it was a bad thermostat.
In a C6, weak batteries are the number one cause of broad-spectrum electrical freakouts like the one you're experiencing. You should be certain the battery is good before chasing down other possible problems.
In a C6, weak batteries are the number one cause of broad-spectrum electrical freakouts like the one you're experiencing. You should be certain the battery is good before chasing down other possible problems.
Because I charge it all night and on my optimate6 charger all was apparently ok.. But you maybe right, I just see that the batterie is 8 years old !!
Here is my video, sorry it's in the wrong way, but was in the good way on my computer don't know why..
Well the video certainly shows what you describe perfectly. With all that weird **** going on I would still think its a voltage problem and replace the battery. Especially if its 8 years old. Thats way past normal life for a battery in these cars. I noticed after that hard start you had a check engine light. Might want to scan for codes and see what shows up.
Well the video certainly shows what you describe perfectly. With all that weird **** going on I would still think its a voltage problem and replace the battery. Especially if its 8 years old. Thats way past normal life for a battery in these cars. I noticed after that hard start you had a check engine light. Might want to scan for codes and see what shows up.
Yes the battery is maybe a way to start !
The check engine light comes on every time I let the car idle for a while when it's hot ! It came from the catalytic converter, as I read on different topics when the temperature of the exhaust is high the ecu send more gas to cool it and from that the O2 sensor catch more pollution and that sh*t comes on..
Same thing on the Z06 of a friend of mine.
But this time it came on from the coolant freakness for sure, but don't have a code reader :/
Will see if a new battery helps..
What are you thinking about testing the different ground wires ?
You could start with that. Make sure the battery connections are clean with no corrosion anywhere. Take them off and sand them along with the battery posts and make sure they dont move at all after you tighten them down. Your battery is in the rear of the car, right? I dont know where its grounded on the car back there since mine is under the hood. If you do get a new battery put it on the charger for a while before installing it.
You could start with that. Make sure the battery connections are clean with no corrosion anywhere. Take them off and sand them along with the battery posts and make sure they dont move at all after you tighten them down. Your battery is in the rear of the car, right? I dont know where its grounded on the car back there since mine is under the hood. If you do get a new battery put it on the charger for a while before installing it.
Happy easter everyone
Concerning the battery connection they are all fine ! I disconnect them oftenly when I don't drive the car for more than a week or two so I check them every time.
Yes the battery is in the trunk, I think she grounded under the hood in the front like yours with a long cable because you got a charger/booster connecter spot near the fuse box.
But what let me crazy about that, is that I already experienced some bad batteries in other cars and there was no way to start the engine with it, plus the optimate 6 is a really good micro-processor charger and catch it when you connect a bad one to it..
And for the little story about that, one day the + from the battery came loose while I was driving because of hard accelerations and bumpy roads. Car was in limp mode sundenly and won't start again after that (because it was loose) but otherwise no problems !!
With the car cold, pop the plug and take a ohm reading off the ECT, then plug the connector back in.
Note to make life easy, to pull the fuel rail cover on the drivers side, get a Fuel line coupling tool, pop the fuel line off the hard connector at the fire wall, and lift the cover off the engine and the disconnected fuel line through the slot. The reason for this, although the cover has a slot, if the cover is cold, it will want to crack before the slip opens wide enough to allow the braided fuel line to slip throught.
Let the car warm up again until you get the temp hot warning, then pop the connector and take another ohm reading (should be a lot lower since the ohm reading through the ECT drops down/ has less resistance the hotter the sensor gets).
The working ohm range of the sensor is 1400 ohm when it's stone cold, to 55 ohms when the engine is brazing hot instead. So on that note, if you are getting a Ohm reading on the sensor around the 100 ohms range with the sensor cold off the two sensor pins, its the sensor that has gone south. (read should be in the 1K range with the engine cold instead).
Also, when you first pop the plug off the ECT, take a reading with a multimeter from ground to each one of the connectors on the plug. This will weed out if the wiring harness has wires that is burnt through before the ECM and grounding out and why the temp gauges are freaking out).
Note, since both the DIC and the temp sensor are both freaking out, the problem is from the ECM back to the sensor, and not from the ECM to the gauges instead).
If the sensor needs to be change, then you will need to drain the radiator coolant down do to do this, since as you remove the sensor with the coolant level still high, coolant is going to be rushing out the sensor threaded channel. As for installing the new sensor, sealer P/N 12346004 (teflon dope, not teflon tape) on the threads of the sensor, and the sensor gets torqued to 15ftlbs.
Also, can not tell if your video is from a cold engine start, or if the engine is warmed up instead. If cold and you are getting this, then suspect the sensor. If the engine is hot, the sensor is fine, and your getting a run away on the heat instead, suspect either that the coolant thermostat is not opening up/sticking closed, or that the water pump internal turbine fan is not longer tight to the shaft, and the although the outer pulley is still turning with the belt, the internal turbine blade is not turning instead (read time for a new water pump).
Note, if someone shoved stop leak into the coolant system for some reason, bank that it has cased the temp problem as a side effect.
With the car cold, pop the plug and take a ohm reading off the ECT, then plug the connector back in.
Note to make life easy, to pull the fuel rail cover on the drivers side, get a Fuel line coupling tool, pop the fuel line off the hard connector at the fire wall, and lift the cover off the engine and the disconnected fuel line through the slot. The reason for this, although the cover has a slot, if the cover is cold, it will want to crack before the slip opens wide enough to allow the braided fuel line to slip throught. Fuel Line Disconnect Tool - YouTube
Let the car warm up again until you get the temp hot warning, then pop the connector and take another ohm reading (should be a lot lower since the ohm reading through the ECT drops down/ has less resistance the hotter the sensor gets).
The working ohm range of the sensor is 1400 ohm when it's stone cold, to 55 ohms when the engine is brazing hot instead. So on that note, if you are getting a Ohm reading on the sensor around the 100 ohms range with the sensor cold off the two sensor pins, its the sensor that has gone south. (read should be in the 1K range with the engine cold instead).
Also, when you first pop the plug off the ECT, take a reading with a multimeter from ground to each one of the connectors on the plug. This will weed out if the wiring harness has wires that is burnt through before the ECM and grounding out and why the temp gauges are freaking out).
Note, since both the DIC and the temp sensor are both freaking out, the problem is from the ECM back to the sensor, and not from the ECM to the gauges instead).
If the sensor needs to be change, then you will need to drain the radiator coolant down do to do this, since as you remove the sensor with the coolant level still high, coolant is going to be rushing out the sensor threaded channel. As for installing the new sensor, sealer P/N 12346004 (teflon dope, not teflon tape) on the threads of the sensor, and the sensor gets torqued to 15ftlbs.
Also, can not tell if your video is from a cold engine start, or if the engine is warmed up instead. If cold and you are getting this, then suspect the sensor. If the engine is hot, the sensor is fine, and your getting a run away on the heat instead, suspect either that the coolant thermostat is not opening up/sticking closed, or that the water pump internal turbine fan is not longer tight to the shaft, and the although the outer pulley is still turning with the belt, the internal turbine blade is not turning instead (read time for a new water pump).
Note, if someone shoved stop leak into the coolant system for some reason, bank that it has cased the temp problem as a side effect.
Hi Dano !
Wow, what a post, thanks a lot man ! Really appreciate that you took the time to explain me that complet sherlock holmes process.
Concerning my fuel rail corver, it's already broken but not from this time ! Will buy that tool for sure.
2 days ago I ordered the OEM Ac Delco coolant temp sensor as I changed the old one with an after market part to be sure if there is a problem with it or not. But your testing technique is pretty interesting. I'm not bad in mechanic but pretty lost in electrical things.
Note that I haven't drained the coolant after the after market sensor remplacement, as I readed on the net that it's not necessary when you just change the sensor.. Is it a mistake ? (air bubbles or so on!?)
Concerning the video, the engine was stone cold when I firt started it (first start of the day) and as you can see around 70°C it start to freakin out (normal driving temp is around 90/93°C to give you an idea).
Will keep you posted for sure. I'm now waiting for the sensor (have no ohm meter) and will find one to do the "gound" test if it's still not working properly. Will buy me a new battery as well, she's old in every way.
Let me just now about the coolant draining, if I absolutely have to do it and if yes, what's the procedure ?
Basic (read cheap) multimeter will work for the ohm resistance check to see what the resistance is across the ECT sensor to tell you if its it is out of range or not. The replacement may be out of range for resistance values, but if not once you test is to make sure, better guess would be in the wiring or ECM.
Note, check the old one's against the new ones. If you are getting the same ohm resitance from the orignal one, the after market replacement, and even the new AC delco unit, the sensor is not your problem.
Replacing the ECT will allow for some fluid lose to create a air pocket in the head (which the ECT will warm up fast since it only seeing the metal contact of the head, and no water flowing across it), but so long as the T stat has an air weep hole, the air trapped in the heat should be pushed out of the system at start up and back in the tank before the T stat fully opens (no weep hole, and the air is trapped until the T stat opens, and then the water now moving through the system can flush the Air pocket out, and pull fluid back in from the tank).
The brass thing in the T stat collar flange is the air weep hole (gets mounted top dead center when the T stat is installed in the water pump channel), and for some reason yours T stat did not come with the air weep hole, pull the T stat, then break out a 1/8" drill bit and drill a hole through the collar in the same location, which is TDC of the collar when the stat is mounted in the water pump.
Without the weep hole, the air is trapped until the T stat opens, and then the flowing water will push the air out of the system.
So on that note, the problem could be just a Air bubble in the head if you have a none weep hole T stat, and until the T stat opens, it going to flake out the ECT.
As for the wiring, try this unit you get a mulit meter.
Unplug the ECT connector, and put the car in to run mode without the car started (hold the run button for around 10 seconds with your foot off the clutch/brake).
You should get a P0116 to P0118 codes since the sensor it not plugged in/ the ECM can not see it, and the temp gauge should not be pinned to the right.
P0116 Engine Coolant Temperature (ECT) Sensor Performance ECM
P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage ECM
P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage ECM
If you are not getting a code, then the wiring has a short in it, and this is what is giving the ECM a Resistance value instead with the ECT unplugged (this slight short, plus the Resistance across the ECT when plugged in itself, is cause the ECM to see the lower resistance; make the ECM think that the coollant is hot when it not.
If such is the case, then start going through the wiring harness back to the ECM to look for the wires melted together somewhere to case a slight short, and if push comes to shove, pull the connectors off the ECM to clean them them with Electrical contact cleaner.
Note, if you had a dead short between the two wires, the car should be throwing a code. Since it a lower resitance instead, makes me think that the problem is a corrosion problem instead.
Also to point out, with the ECM unplugged, go back and check the ECT connector wires again with the multimeter. There should be no resistance across these two wires of any kind (read first check with the wired still connected to the ECM and ECT unplugged, may show a slight resistance from the ECM circuitry itself).
The ECM is the silver finned box, and you get to it via pulling the back passengers wheel cover with the tire removed.
Now the fun one, and the problem could be corrosion in the ECM instead. It could be across two of the pin in the socket that is resolve via just cleaning the sockets with you clean the connectors with spray contact cleaner with the ECM still screws in place, or it could be in the ECM board instead.
Note, when you look at the ECM sockets with the connectors disconnected 9and just the area of the ECM), will be able to tell real quick if it was water logged/looks like it was stored in a fish tank (pins will be corroded). Why GM desired to put the ECM outside the car, low in the fender void is beyond all of it. Hence it the reason that every one jokes about driving in the rain, having to go through any standing water puddle; but is the the true fear instead of drowning the ECM and it's connectors. If you look at the above photo, you can tell the the fender void area in this car has seen a lot of water.
If everything checks out good, such as the wiring harness fine, no air trapped in the coolant system, The ECT sensor good, and the connectors/socket pins cleaned on the ECM, then I can take you down the rabbit hole of pulling the ECM apart so you can Spray contact clean it's internal parts if the problem is there.
And again, the Temp dial gauge, and the DIC are both agreeing on each other (ECM thinking that the water is hot), so the problem is from the ECM back to the ECT.
Basic (read cheap) multimeter will work for the ohm resistance check to see what the resistance is across the ECT sensor to tell you if its it is out of range or not. The replacement may be out of range for resistance values, but if not once you test is to make sure, better guess would be in the wiring or ECM.
Note, check the old one's against the new ones. If you are getting the same ohm resitance from the orignal one, the after market replacement, and even the new AC delco unit, the sensor is not your problem.
Replacing the ECT will allow for some fluid lose to create a air pocket in the head (which the ECT will warm up fast since it only seeing the metal contact of the head, and no water flowing across it), but so long as the T stat has an air weep hole, the air trapped in the heat should be pushed out of the system at start up and back in the tank before the T stat fully opens (no weep hole, and the air is trapped until the T stat opens, and then the water now moving through the system can flush the Air pocket out, and pull fluid back in from the tank).
The brass thing in the T stat collar flange is the air weep hole (gets mounted top dead center when the T stat is installed in the water pump channel), and for some reason yours T stat did not come with the air weep hole, pull the T stat, then break out a 1/8" drill bit and drill a hole through the collar in the same location, which is TDC of the collar when the stat is mounted in the water pump.
Without the weep hole, the air is trapped until the T stat opens, and then the flowing water will push the air out of the system.
So on that note, the problem could be just a Air bubble in the head if you have a none weep hole T stat, and until the T stat opens, it going to flake out the ECT.
As for the wiring, try this unit you get a mulit meter.
Unplug the ECT connector, and put the car in to run mode without the car started (hold the run button for around 10 seconds with your foot off the clutch/brake).
You should get a P0116 to P0118 codes since the sensor it not plugged in/ the ECM can not see it, and the temp gauge should not be pinned to the right.
P0116 Engine Coolant Temperature (ECT) Sensor Performance ECM
P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage ECM
P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage ECM
If you are not getting a code, then the wiring has a short in it, and this is what is giving the ECM a Resistance value instead with the ECT unplugged (this slight short, plus the Resistance across the ECT when plugged in itself, is cause the ECM to see the lower resistance; make the ECM think that the coollant is hot when it not.
If such is the case, then start going through the wiring harness back to the ECM to look for the wires melted together somewhere to case a slight short, and if push comes to shove, pull the connectors off the ECM to clean them them with Electrical contact cleaner.
Note, if you had a dead short between the two wires, the car should be throwing a code. Since it a lower resitance instead, makes me think that the problem is a corrosion problem instead.
Also to point out, with the ECM unplugged, go back and check the ECT connector wires again with the multimeter. There should be no resistance across these two wires of any kind (read first check with the wired still connected to the ECM and ECT unplugged, may show a slight resistance from the ECM circuitry itself).
The ECM is the silver finned box, and you get to it via pulling the back passengers wheel cover with the tire removed.
Now the fun one, and the problem could be corrosion in the ECM instead. It could be across two of the pin in the socket that is resolve via just cleaning the sockets with you clean the connectors with spray contact cleaner with the ECM still screws in place, or it could be in the ECM board instead.
Note, when you look at the ECM sockets with the connectors disconnected 9and just the area of the ECM), will be able to tell real quick if it was water logged/looks like it was stored in a fish tank (pins will be corroded). Why GM desired to put the ECM outside the car, low in the fender void is beyond all of it. Hence it the reason that every one jokes about driving in the rain, having to go through any standing water puddle; but is the the true fear instead of drowning the ECM and it's connectors. If you look at the above photo, you can tell the the fender void area in this car has seen a lot of water.
If everything checks out good, such as the wiring harness fine, no air trapped in the coolant system, The ECT sensor good, and the connectors/socket pins cleaned on the ECM, then I can take you down the rabbit hole of pulling the ECM apart so you can Spray contact clean it's internal parts if the problem is there.
And again, the Temp dial gauge, and the DIC are both agreeing on each other (ECM thinking that the water is hot), so the problem is from the ECM back to the ECT.
Hi Dano,
Got me a multimeter and checked the battery voltage with and without the car in run mode ! 12,32 volts without and 11,77 volts with it !
As I fully charged it last week, I think there is a problem with this battery also. So I ordered a new one yesterday, will be delivered this week.
I also checked the voltage between the front + (next to the fuse box in the engine bay) and the ground pin of the ECT plug, voltage is the same as on the battery so the wiring seems to be ok.
Concerning the ECT sensor,I received the new one, but I don't have a second plug to test it and contrarily to the US where you will find anything you need, here in France you simply find nothing.. So will wait on the thermostat and change both in the same time.
Turn the dial on the multimeter to 2000 Ohms (horse shoe symbol) then using the wire probes (red and black), put each one on each one of the pins of the ECT socket.
This will give you the Resistance Ohm reading through the ECT's themselves, and if all three match in readings, then the problem is not the ECT sensor's.
If you want to check for a short in the wires, then switch the dial to the the diode setting instead and put the red/black probes on each one of the metal receptors for the ECT pins in the harness connector instead.
Here, A 0-Zero reading on the gauge means no short between the wires, while any number on the gauge means it has a short between the wires instead.
Got me a multimeter and checked the battery voltage with and without the car in run mode ! 12,32 volts without and 11,77 volts with it !
As I fully charged it last week, I think there is a problem with this battery also. So I ordered a new one yesterday, will be delivered this week.
I also checked the voltage between the front + (next to the fuse box in the engine bay) and the ground pin of the ECT plug, voltage is the same as on the battery so the wiring seems to be ok.
Concerning the ECT sensor,I received the new one, but I don't have a second plug to test it and contrarily to the US where you will find anything you need, here in France you simply find nothing.. So will wait on the thermostat and change both in the same time.
Keep you posted probably saturday or sunday.
A big thanks for your precious help man !
You mention the analog gauge but you don't mention what is happening with the coolant temp display on the DIC. If it isn't jumping around like the analog gauge is then your problem may not be the battery and its state of charge. Also what is happening when you display coolant temp on the HUD?
You mention the analog gauge but you don't mention what is happening with the coolant temp display on the DIC. If it isn't jumping around like the analog gauge is then your problem may not be the battery and its state of charge. Also what is happening when you display coolant temp on the HUD?
Bill
Hi Corvette lovers !!
So, just came back from the Vette, new battery is in place and new OEM coolant temp sensor in place too.
Start it, (started better than with the old battery) and let it warm up. Temp climb to 56°C and the exact same problem is still there.
Bill to answer you, the coolant temp on the DIC display show the exact same thing as the gauge.
After that, I shut the engine off and removed the thermostat to test it. Because I noticed that the hose connected to the water pump was cold and all the others were hot. I put the thermostat in boiling water and it opens but I don't know if it properly opened or not (here is a picture of it)
Let me know if you think it's enough open or not, because it will not open more than that, and before the water was boiling it was closed..
But the problem happen before it should open so I don't think it come from the thermostat at all..
Will receive the new one tomorrow, will test it to see ! Otherwise the next step is the ECU but it's 1 and a half year old so I don't think it already bad !?
Just think about one thing while I'm on google trying to get more info about my problem !
Is there one or more fuse who are related to the cooling system or so on ??
I'm pretty sure there is a short somewhere in the wiring harness..
And it remember me that this afternoon, just after replacing the after market sensor by the new OEM one I forgot to re-plug it before I start the car and of course the DIC display tells me directly "Coolant temp XXX" and I was like s**t I forget to plug it back.
So I shut off and plug the connector back in ! Started again and all was fine until it reach 56°C where the needle climb to 120°C and tells me "change engine oil" again, then back to normal around 68°C at this moment ,then back to max temp and then falls to zero and stay there ("Coolant temp XXX") (like if it's unplugged) and each time it goes to zero, it will always stay there, no more needle move.
Replaced the thermostat and test it in boiling water before I installed it. React exactly as the old one (good), and as I expected, problem still there.
Was with my buddy to do it, as I was in the car he filled with coolant.
So next step is the ECU/PCM (don't know how you call it), will remove it tomorrow, spray it and see what happens.
Apart from that, car started perfectly the first time and after the coolant fill I shut it off and restart it 2 times to see what happen, and man it had pain to start and you can feel in the way it start and the way the engine runs that there something wrong with the electronic.
Hatch Ajar message, Change Engine Oil still there directly (really strange, like a crazy pcm)
According to my buddy, the PCM is the culpable (PCM it self or connection as Dano said).
That said, it make me remember that the last time I run the Vette (before the problem happened) Went for a quick ride to get me some car shampoo to wash it, came back home and washed it by hand and with the help of my power washer as usual.
Because we planned to go for a shooting with a friend of mine the next day. And just after I washed it, I put it back in the garage, and that f**king problem started the next day before the planned photo shoot.
So I really start to think about water in the pcm connections or in the pcm it self, because it just next to the fender grille and I remember passing by there with the power washer (will never do it again).
Will keep you posted guys. (Sorry for the long story but it's the only way to explain the sh*t and find the fix).
Good evening everybody (yes it's around 11pm here in France),
As promised, I keep you posted and I finally find the problem !
So this afternoon as planned I disconnect and removed the PCM, to spray the connection as well as the interior of the PCM it self.
Work it the first time, and after a little break, problem was back !
So I tested a lot of things the entire afternoon between the PCM, wires, connector as well as an other PCM to see if it was the culpit but it wasn't.. And finally I deduced that it couldn't be another culpit as the wiring harness itself by the results of all the test.
But at that point I had to know WHERE is that snapped wire.. And a little bit by luck (I have to admit it) I found the spot by jiggling the wiring harness just between the fire wall and the engine on the passenger side. By doing that, the coolant temp was switching on the DIC display between "XXX" and the actual temperature.
Here is a picture of it :
Right here on the junction, will pull that sh*t out tomorrow and see what's wrong.
04-03-2015, 06:29 PM
Crazy coolant gauge
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but not from this time ! Will buy that tool for sure.
