Radiator Fan Runs when Car is Off Forever - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
Problems and Service Talk about any mechanical problems you are having

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post #1 of 83 (permalink) Old 05-08-2012, 04:17 PM Thread Starter
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Exclamation Radiator Fan Runs when Car is Off Forever

I just bought a 05 Cobalt LS all black yesterday! beautiful car

Car is not inspected I got a ten-day.

I have engine codes P0480/481.

Basically... the radiator fan runs all the time with the car on and when the car is off, will run till battery dead. What the guy did that I bought it from was "remove the cooling fan relay II" to shut off the fan.

Fan still turns on at 151 and coolant temp is usually 190's running temp, but I cant get it inspected unless I figure out this issue.

Now if you plug in the relay with the car on or off, it buzzes and makes noises - this I don't remember it doing when he showed me. Already tried a different relay, same thing.

I've been reading google for the entire day here, I'm hoping someone here can help.
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post #2 of 83 (permalink) Old 05-08-2012, 05:05 PM
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Which engine? I presume 2.0liter.

---------- Post added at 09:05 PM ---------- Previous post was at 08:46 PM ----------

Make sure your A/C,fan motor and windsheild defog is off when you do this test. When Cobalt is cold and you re-intall the relays do the fan start right away? If they start then I'm affraid your PCM might be fried. It is the PCM that sends a ground to fan relay1 and fan relay2, also PCM that sets the DTCs P0480 for fan 1 circuit malfuction and P0481 for fan 2 circuit malfuction .

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post #3 of 83 (permalink) Old 05-08-2012, 05:13 PM Thread Starter
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a/c and defog are off, cold start. yes, put relay in and fan starts right up.

could it be PCM or ECM, ive read a lot of things and ECM was brought up quite a bit. Unless they are the same thing.

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post #4 of 83 (permalink) Old 05-08-2012, 05:25 PM
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In a 2005 it is called a PCM. If it starts right away chances are the 2 drivers for your relays are shorted out and since GM doesn't repair these you will probably need a new one or junkyard one. It will also need to be re-programmed to match the VIN# of the vehicle. But to be on the safe side don't take my word for it get it checked by a Tech 2 mechanic. He can go into the PCM GMLAN and activate and deactivate the fan relays with the tech 2 controller. If he can't then you know for sure these drivers are bad.

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post #5 of 83 (permalink) Old 05-08-2012, 05:35 PM Thread Starter
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hmmm you could be right! thank you, will have to check into this
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post #6 of 83 (permalink) Old 05-08-2012, 07:45 PM Thread Starter
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coby where you at!

do the serial numbers have to match for the PCM, if I got a used one?

my number is: 12597328 yk77

and check this out, this guy has the same issue I do, AND THE SAME PCM NUMBER.

http://www.*************/forums/2-2l...7/#post5579627
EDIT: url is blocked or whatever, Im new and dont know the rules, its just a post that says:

So the cooling fan circuit in my car decided to mysteriously short to power which melted down the ground portion in the PCM and causes the Fan to be on all the time while driving and when ever it feels like when its off. i've dealt with it for a while but i can tell the fan is now starting to crap out. checked w/ the dealer and they charge $313 for the part, $156 for the flash/repro, and $212 for labor "because they have to put it in". since i cant get my hands on a tech2 with the flash/repro software on it i was considering a used PCM. the only thing is that i cant seem to figure out if the used PCM will talk with everything else on board. i know there are different PCM part# due to select features but i had heard that they are serial number specific and may need to flashed to match. just wondering if anyone has ran into anything like this before or heard anything.
thanks.

05 LS
PCM #12597328 (12599714)


shame no one ever replied...
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post #7 of 83 (permalink) Old 05-08-2012, 08:10 PM
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I guess he's saying what I dedeuced. Canada man, Moncton eh!

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post #8 of 83 (permalink) Old 05-09-2012, 05:06 PM Thread Starter
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disconnected the pcm one by one while the car was off then put in the relay, fan still turned on.

had my buddy's father check it out, hes an electrician. I told him my next idea was that it could be the cooling fan motor has a short in it. He didnt think that would be the issue. Basically thinks the problem lies within my wire harness.

He took out the 30A fuse for cooling fan II and popped the relay in, no chatter.

Not idea if the code will clear with this method.

Still not 100% if the PCM is ruled out.

we checked the resistence on the new relay I had versus the old. Turns out the stock relay is worlds better.
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post #9 of 83 (permalink) Old 05-09-2012, 05:10 PM
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Nothing wrong with fans or their harness because when you pull the relays they stop. Might be corrosion on the connector at the bottom of the fuse block.

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post #10 of 83 (permalink) Old 05-09-2012, 05:24 PM Thread Starter
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will be checking that one friday
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