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Discussion Starter #1
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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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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Discussion Starter #3 (Edited)
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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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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Discussion Starter #6
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-l61-performance-tech-45/pcm-interchangability-242397/#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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I guess he's saying what I dedeuced. Canada man, Moncton eh!
 

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Discussion Starter #8
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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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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Discussion Starter #11
I got an idea!!!

there are three wires from the cooling fan to the relay. Purple which is low speed, blue which is high speed, and white which is ground.

Saw on another forum that you can bypass the relays and add a switch. If so then i'd just splice the blue wire to power, then to a fused switch in the cabin, so I could turn on the fan at will. If it still sorted, then it would have to be the PCM, or white ground wire.

car runs fine with cooling fan #1, I'm always <200.

My only question is, if I add a switch to high speed, will it throw a CEL?

just trying to get rid of the code so I can get an inspection.
 

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You will still get the code because you have a fan circuit malfunction. Please don't try to jimmy it. Fix it or get it fixed. Take the time,disconnect your battery,remove underhood fuse block and inspect it. If it can't be cleaned or repaired get a good second hand one and replace it.
 

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Take Cobys Advice, someone rigged the fans like this on a Ford Focus I was working on, it was a few days to undo their crappy wiring, it was $200 for that, but instead of having a switch which burns out a few times a month at least, because only high speed works on it (will happen to you too), then also, you may forget to turn it on, or off, you end up with crap. After I made the repair on the Ford Focus, I now get 2 speeds controlled by the coolant temp sensor and AC rather than having to rely on somebody switching something on then off after.
 

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Discussion Starter #14 (Edited)
I'm trying to avoid the dealer can't you tell :nahnah

Yesterday we checked the wires from the fan to the fuse box, one by one for continuity and resistance - this would check for shorts. All wires are just fine.

We then confirmed that the top left corner or 1st quadrant of cooling fan relay #2 is the wire for pin 43 PCM. That wire was checked and everything is ok.

We then checked each of the four slots for power and grounds, and found that the 4th quadrant is most likely the shorted wire.

Rigged a relay with wires and put the 4th quadrant to a new ground on chassis, fan didn't go on and no relay chatter! On second ignition a CEL was thrown.

Will know by Monday if I can get a hold of a tech 2 to test the drivers for the PCM.

I still got finals this week, so this is a pain in the ass. Were 60% sure that the PCM is fried :(

anyone know how much this would cost? I can't find any online with matching numbers.

If I can't get the tech 2, I'll be heading to the dealer.

EDIT: note that we couldn't check the circuit board for the fuse block, not going to rip it apart. All connections seemed fine.
 

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Sorry to say that dealers are almost the only guys with Tech2s. So you are going to need to go there sooner or later unfortunately.
 

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Viper, I was able to find a Tech2 by calling around to local shops. Believe it or not, some of the smaller independent ones have them. Sometimes all it takes is throwing a few bucks and/or a case of beer.

Coby could probably answer this, but is programming a new PCM even possible for an end-user with a scanner? I have no idea what authorization, database or other, that GM requires for that.
 

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Yes, if you have a Tech2 and the factory PCM RAM isn't fried you can dump the PCM data to the Tech2. Then erase the replacement PCM and reflash it from the Tech2. If the PCM is totally screwed then it takes a little more time because you have to enter data step by step, about a 2 hour job from scratch because the Tech2 although high tech is not very user friendly. I downloaded the book just for something to read. It has 728 pages of descriptive information that if you don't have a Tech2 in your hands is pretty much Grec.
 

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Discussion Starter #19
so a buddy of mine let me know of a guy at a shop that has tuner computers.

for $120 he will put a PASS on any code for the first time, and $20 for any codes after that. Or $20 to undo the code

He has a friend with a trans am, no Cat, no smog ect, all codes passed.

I'm looking on getting this car inspected. Think this is a good idea?

Do I really need a high speed?

*runs and hides in case coby wants to smack me*
 

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I can't smack you from way over here,
anyway it is still your decision.
Why don't you put all that cash towards fixing it instead. Win win.
 
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