Hi all,

Have a p0480 CEL and air conditioner does not blow cold air.
Was told that there is actually a technical service bulletin (TSB) and the fix is to replace the fuse & relay box (part number 15269048).

I was going to try replace the relays first, but has anyone come across this? A lot of the threads here are pretty dated.

Thanks

 

Your air conditioner probably won't even run as the ECU knows the cooling fan isn't working. If it does run it will likely build pressure quickly and shut off from inadequate cooling of the condenser.

I'd start with the easy thing and check your fuse. As far as I know the fan is connected directly to the fuse box and the ECU doesn't have any direct connection to the fan power circuit. The ECU is only connected to the coil side of the fan relay so I'd assume the ECU will only detect if the relay coil doesn't have power from a blown fuse or wiring issue or if the relay is bad and is making the circuit open. So after checking the fan fuse, check the relay for function and check the fuse block pins are getting the right readings. My best guess is that if you don't have a wiring short somewhere that you just have a bad relay.

The diagram above to the left is what the bottom of your relay will look like. To test the relay you can energize the coil by connecting pin 85 to ground and pin 86 to positive to complete the circuit (you can also reverse the polarity and it will work the same way). You should be able to feel/hear an audible "click" when this happens. When the coil is energized you should have continuity between pin 30 and pin 87 (but not 87a). When the coil is at rest you should have NO continuity between pin 30 and pin 87 (but will have continuity to pin 87a). You can test the relay with a 12V source and a test light or multimeter. If the relay functions as it should than you know your problem is in the circuit. Either it isn't getting power because of blown fuse/broken wire or bad connection or it isn't getting grounded through the ECM when commanded for the same reasons.

If the relay and fuse checks out the next move is to test the pins in your fuse box when the car is running and the AC turned on but relay removed.

• The terminal that corresponds to relay pin 30 should have constant 12v+ power source. You can check this with test light to ground or multimeter of DC voltage mode to ground.
• Terminal for pin 87 should connect to your fan. You can test for continuity between that fuse box terminal and the main harness fan connector terminal which you can test by disconnecting the fan connector and making contact (harness side not fan side) with the connector terminal directly. I can't tell you which connector terminal is which but one should have connection to pin 87 fuse box terminal and the other should connect straight to ground. If both fan pins have continuity to ground you have a short in the wiring.
• Pin 86 should also have constant power. If pin 86 doesn't have power but pin 30 does than you have a connection issue between pin 86 and the main fan fuse.
• Pin 85 should be grounded through the ECM when the ECM commands the fan on. This is why I instructed to turn the AC on to make sure the ECM commands the fan to be on. Someone else can chime in but I believe the ECM should continue to command ground even after it detects relay fault though I may be mistaken. The only way I know to test 85 connection to ground is with the resistance test mode on a multimeter. You definitely DO NOT want to induce a load to that ground from a positive source even with a test light as it is a very low amperage rated ground through the ECM and you could fry the ECM.

There's a chance Pin 86 and 85 are flip-flopped so check them both for power to ground before further testing on those pins.

I also read the generic definition for P0480 can also trip from a high reading on the AC pressure sensor but I don't know if the Cobalt has this mechanism to trip a fan fault. If it does I would think someone with an appropriate scantool might be able to see if the pressure sensor readings were normal from the freeze frame data captured when the code was tripped.

 

You could just buy this...

 

Thanks everyone for their replies.

Had some time off and started with the basics as recommended. Both 30 amp (Cool Fan1 and Cool Fan2) Jcase fuses were blown. Replaced both of them with 30 amp Pal fuses (not sure if it really makes a difference between using Pal vs Jcase... but the Pal ones look more aesthetically pleasing).

At any rate, the radiator fan now kicks on as soon I put the key in the ignition and the radiator fan will run at max speed. When the car is off it will continue to run for a couple of minutes before turning off. I replaced Cool Fan1 and Cool Fan2 relays. Thermostat and coolant sensor replaced about a year ago.

Initially went from radiator fan not turning on to now being on all the time.
Any other ideas?

 

You'd have to have some wiring issues somewhere. Fuses rarely blow without a short/overload situation and I would say 2 different fuses definitely don't blow at the same time without some other problem. I'd guess you have a short or your fans are overloading the circuit for some reason.

As far as the fans running full time now are you sure you put the correct style of relay? There is a different type that will physically fit but is configured differently. If the relays are correct and working correctly you will need to investigate the pins in the fuse box to determine if it is getting a ground trigger from the ECU when it shouldn't be. Is your thermostat reading correctly on the dash?

 

That's a fair point, however if I had a short wouldn't that cause the fuses to keep blowing?
As far as temperature, yeah it's reading correctly readings range from 170-180F
Swapped back my old relays and still the same deal.

Appreciate all the help so far!
Any other guesses?

 

A vehicle bounces down the road so things rub and shift and many shorts can easily be intermittent and only happen when the conductor shifts just right to make contact with ground. Like I also said the fan could be drawing higher amperage either from fault or some sort of stall condition.

If you don't want to take the time to properly diagnose the circuit issue I suggest

 

Ouch, realistic but 'ouch' .

 

Without OP investigating/testing the circuit we can't narrow down our guesses more than to suggest replacing the fan, engine harness, and ECU. I just get frustrated when people ask for help but aren't willing to put in the effort to figure anything out for themselves.

 

I I had the same problem, I suggest hitting the junk yard getting a Console fan switch. For what ever reason those pins in that control switch Get super hot and melt the plastic around the pins. I suggests pulling yours out an unplugging the control harness under the stereo and checking the pins insideThermostat controls. If ya cant find any, ive got 3 or 4 extras in black an silver? Hope this helps.