Engine cooling fans will not come on?

If you unplug the coolant temperature sensor and the fans come on you know the circuit is good. I would like to know if the ECM is reading the correct coolant temperature.You would need a scan tool that reads live data to check that also a infrared temperature gun to compare actual temperature to what the temperature the ECM is seeing and reading.

If the ECM is not reading the correct coolant temperature then I assume it is a bad ECM? (basically its the only part that I have not changed in the cooling system). so I might as well purchase one instead of buying all this test equipment that may tell me it is bad? Thanks again.

You missed my point. The wiring might be good enough to put the fan into default mode does not mean it is good enough to read the correct values back to the ECM. When I diagnose a problem I always check everything not guess and start replacing parts. If you want to do that good luck to you with replacing the ECM, but I am not telling you it is bad or that it should be replaced at this time. If you are going to diagnose and repair your car the right way you have to buy tools etc., to repair and diagnose it properly. If you need anymore help let me know and I will be more then happy to help you.

Also, a cheap scan tool that reads live data is like fifty something on Amazon an infrared temperature gun is $50.00 or under. Cheaper then an ECM and now you have tools for the time you have a car to work on.

Okay so then what on earth (that I have not all ready replaced with premium NAPA parts which believe it or not are not expensive vs test equipment that will only be used one time). What parts/wiring harness that have not been replaced would cause this? possibly wiring might be good enough to put the fan into default mode does not mean it is good enough to read the correct values back to the ECM.

There are some relays that control the fans. Here are some diagrams that will help you fix the problem.

The coolant temperature sensor and a relay control the fans. If you start and run it with the A/C off do the fans turn on? If no start by replacing the CTS, it is cheap. God bless. Thank you for using 2carpros.

Rasmataz that is much. Cadieman I did change the CTS and they still not come on. That is why I am here. :-)

If you read up further from his first post Cadieman he replaced the coolant temperature sensor fans work with AC and when unplugging the coolant temperature sensor fans come on in default mode. Now to Mikecarwile without without knowing the ECM's coolant temperature readings we do not know what is supposed to be happening relays being grounded etc. I am not even going to begin to start throwing guesses at you for parts you can change. Were here to help you diagnose and repair your car not say replace this, oh, that did not fixed oh try this now. You have two choices get the correct tools to diagnose and repair your car you can take it in for repair. It is hard enough to help people fix there cars over the internet without being able to test anything test drive the car see wires different parts of the car etc. So when i cannot ask you what is the ECM reading versus actual temperature makes it really difficult to help you. I do not guess when i repair cars in front of me or helping people to fix them over the internet.

You sure it is the correct thermostat? remember the CTS reads the engine temperature and the stat controls the temperature. The computer might not be reading it right therefore not activating the fan relay. I guess your last place is the PCM.

Rasmataz, i will compare Napa part number from stat box i still have against what Napa says should be the correct part number. So defective/wrong new stat could be it (not holding anyone to an answer)..

There could be a issue with the wires running from the ECM to the coolant temperature sensor or other variables. Without seeing the ECM values. That is the first place I would start considering the fan turns on when unplugging the coolant temperature sensor. I would not scrape it especially with 80,000 miles on it. You are not bothering us we are here to help people fix there cars. We just do not guess when fixing cars. Like I said the tools are not that expensive and whole cheaper then buying another good used car, those are expensive.

If the stat was opening at too high of a temperature then the coolant would get hot enough for the fan to come on? If the stat opened at too low of a temperature and the coolant did not get hot enough for the fans to come then why is coolant boiling over a brand new cap you replaced?

Saturntech9, it is just frustrating. Did find an infrared temperature gun on my patio (use it to check bar-b-q temperatures) this should work? No just got to figure out whet to point it at on the car. will look at local shops for real time analyzer and figure out where to hook it up to and get what ever it needs to tell us. Meanwhile I found out that I should be able to drive it until it get sorted out just need to make sure the A/C runs all the time. :-)

I know it is frustrating even the pros like us get frustrated with cars, lol. I do not know anything about your bar-b-q thermometer so i cannot comment on if it would would work. But where I would measure the temperature would be on the head right where the upper hose attaches. Here is a link to a scan tool that reads live data locally you will probably spend way over $100.00 for one:



http://www.amazon.com/AutoLink-CAN-OBDII-Code-Reader/dp/B001R5K2W8/ref=wl_it_dp_o_pC_nS_nC?ie=UTF8&coliid=I550IMQ2KTG23&colid=18P9GG85XVI37

Test the coolant for hydro carbons to check that it has not a blown head gasket. They sell a kit at the parts store.

just ran car for twenty minutes at idle. Radiator hose going to thermostat felt soft and empty but hot. Could the new thermostat be bad and not opening properly? Heater works great. Still no fans.

Like i said before if the thermostat was opening too late or even not at all the fan should turn on before it boils overs.

Been running fine with A/C as the cooling fans come on. Turn A/C off and it spits every time and my gas gauge goes up to full and stays there no matter how low the tank is.

How long has the gas gauge been acting up? What codes do you have in the computer?

About same time the fans stopped working, but really never noticed until lately. Zero codes in computer.

If you bounce the car will the gas gauge needle move off of full? Most common reason for fuel gauge issues are bad fuel sending units.

When i went back to check this it was at the quarter mark (where it should be) started up and stated there. Now this am it has a new problem. Filled water reservoir back up to full cold mark with 50/50 premix. Drove car with A/C on and cooling fans running noticed within five minutes that temperature was climbing faster than normal. After about two miles the temperature went higher than it has ever been and coolant started blowing out the res tank (A/C on and cooling fans were running) and noticed that the gas gauge needle was bouncing from full to empty back and forth. Turned around and drove back home parked it.

Would be nice to know the temperature of the coolant and what the coolant temperature sensor is reading etc.?

I will get it tomorrow. Thanks.

Have we checked for a blown head gasket yet? Since now it is heating up with the fan running constantly. Also, is there a lot of air being pulled through the radiator fan?

Let me jump in here. I see this question a lot from people and most of the time there is no problem with the fans at all. Although the thermostat is set to 195 degrees and when the car is moving, it will usually maintain that but when stopped and relying on the fans, it is supposed to run much hotter.
This car has a two speed fan system and even low speed does not come on until about 225 degrees and high speed is near 230. If you lost low speed only, it would be very late coming on. It still needs to be tested thoroughly for a blown head gasket because that will make it boil over before even hitting fan temperature.
The first thing you need to do is monitor the fans and temperature through a scan tool to know exactly what the fans are doing.

Thanks for the suggestions Wrenchtech he is getting a scan tool and temperature gun to check those things tomorrow. As far as the head gasket test goes AutoZone rents a chemical tester for free you just have to buy the fluid.The fluid is about $8.00.

I have never had very good luck with those testes myself. The scan tool will tell you if there really is anything going on. It is also very difficult to get all the air bled out of the system on this car.

I only have working fans (low and high speed) when the water temperature sensor is removed or A/C is running. I ran the AC it did not overheat at all. It only started to boil out of reservoir tank with A/C running (which gave me my radiator cooling fans on) last night. No water in oil. Maybe the thermostat I changed is bad and it is stuck.

You do not know that. You need to see the digital temperature in the computer.

Also, a weak or bad radiator cap can cause a boil over even when it is not overheating.

I have replaced the radiator cap twice. they always separate into two pieces (the part that has the o-ring which fits tight into the reservoir and the screw cap itself.

Would the radiator cap separating into two pieces make a difference? The main part with o-ring seal fits real tight it just the top plastic screw cap that comes off.

Yes, I would change it because it needs to hold pressure to work right.

Please let us know happens so it will help others.

I have Traverse 2012. Temperature gauge is going little up and then come down. This situation occurred in heavy traffic or vehicle is not moving. I changed the thermostat but no luck.
I used the scan tool (elm) when temperature reached 105C then fans turn on. speed is same as i turn on the AC. So it means fan is not running on 95C which is slow speed fan.

What is the solution?

First item I would check would be the low speed fan relay number one and its fuse. If both are good then check that relay three is working as it passes the power through to the second fan. If that is okay as well follow the wiring from the fan and look for any broken or rubbing wires.

The system works by first turning on both fans as a series circuit using relay 1. That feeds battery voltage through both motors and they turn at low speed. Once the temperature threshold rises the ECM then triggers relays 3 and 2. Relay 3 now creates a direct ground path for fan one and relay 2 powers up and feeds full battery power to fan 2.

Yesterday I used LED's on fan relays to check the behavior.
When temperature reached at 105C then relay one turn on and fan also turn on. I removed relays one by one. Only FAN2 relay is not changing the fanbehavior. See the image.

My friend has Acadia. I monitored his car temperature through scanner. When temperature reached at 105C fans turned on but temperature gauge is steady. So it has prove that my Traverse is not overheating or fans are switching on delay. Now problem is gauge is moving when temperature rise 103C. Is it gauge problem or some thing else?

Normally the fan operation will cause the temperature to cycle and the fans cycle with it. So the temperature rises, the fans turn on, this cools the system to a temperature below the on temperature and the fans go off. The coolant then absorbs more heat and the fans come back on. The temperature gauge should cycle with it. Unless there is an issue with the cooling system the temperature shouldn't stay steady like your friends. It should normally cycle.

If fan turns on normal temperature which is 105°C then gauge should be steady. If gauge is rising after the fan switch on and temperature is also increasing then we can say it is cooling system problem.
May be Traverse normal temperature is 100°C or ECU is giving wrong value to temperature gauge. It all happened after cleaning the throttle body, I do not know it has some link or is a coincidence. :-D
It is hard to believe that problem is in cooling system, check the image of thermostat which I replaced, it is clear like new. No rust and dirty and I filled proper coolant.

What should I do to diagnose this problem? Temperature sensor can be a problem?