2008 fan control circuit problem

[zr440]

My 2008 3.8 is giving P0480 code. It was also giving another code which replacing the tstat fixed. The P0480 code remains. I have hooked up the fan that doesn't come on to power and it works fine. Today I tried replacing the temp sending unit and that didn't change anything. Although after I drove it for a few miles my temp gauge quit reading. The gauge cycles on startup but then remains at the bottom. It seems unlikely that a brand new temp sender would work and then fail so fast though. I'm lost at what to try next. Any ideas?

[zr440]

Forgot to add I have swapped relays between fan 1 and 2 with no luck. I also swapped the two large 30a fuses for fan 1 and 2 with no change there either. Fan 1 always remains off.

[tblake]

P0480 - Cooling fan relay 1 control circuit

If I remember correctly, the PCM controlls the ground to this relay. Check for voltage at the relay socket, and if no voltage, check your fuses.

[zr440]

Are there other fuses besides the two big 30 Amp ones? I swapped the fuses between Fan 1 and Fan 2 and Fan 2 still works so those fuses should be good. I think it was spot 31 and 32 or something under the hood

[zr440]

Well my temp gauge came back and is working fine. Fuses are all fine, relays are new, sending unit is new, thermostat is new, and FAN 1 works when hooked to power directly. I have looked over the wiring and I don't see anywhere that it could have possibly shorted or anything. It all looks brand new under the hood still so I am confused as to why FAN 1 will not come on and keeps throwing the code.

[tblake]

Disconnect the battery, and remove the PCM connectors to check for corrosion on all the pins.

[BNaylor]

Originally Posted by zr440

My 2008 3.8 is giving P0480 code.

How many miles do you have? Any warranty left?

[zr440]

Warranty is up. About 110,000 miles on it now.

[zr440]

I took a look at the connectors on the ECM, there is no corrosion at all. I looked all over for any kind of breaks in the wiring between the fan and ecm and fuse panel and I have not found anything. I cleaned up the battery cables, checked the fuses and relays again. I'm wondering if the ECM could be bad, but wouldn't that cause other problems as well?

[BNaylor]

There are two conditions for setting off the P0480 DTC which is the cooling fan relay 1 control circuit.

1) Improper voltage level detected for the cooling fan relay circuit.
2) Condition present for a minimum of 30 seconds.

So there is either a short to ground, open/high resistance or short to voltage in that circuit. The ECM/PCM supplies a ground to the respective relay to energize it to turn on the respective cooling fan. Is the fan not turning the left fan?

On cooling fan relay 1 check pin 87 which is the output to the fan. Should be 12 volts which is passed directly to the fan. If 0 volts then the relay is not energizing. So next check for 12 volts (B+) at pin 85 of the relay which should be there at all times or with ignition to ON. Pin 86 is the ground from the PCM. Also, cooling fan relay 2 passes a ground to the cooling fan direct (Pin A) at the fan so check that too.

[zr440]

The driver side fan is not turning. I have swapped relays between fan 1 and fan 2 with no change. I will try your suggestions and see what I find.

[BNaylor]

Originally Posted by zr440

The driver side fan is not turning.

The driver's side is the left. If you need any further assistance let me know including wiring diagrams since I have the GM '08 Grand Prix Base/GXP models Factory Service Manual. Good luck!

[zr440]

I figured it out. The plastic cover on top of the engine had rubbed into the wiring harness. I had to twist the harness a little to see the bottom side of it. Soldered two broken wires back together and it works

[doctorhrdware]

To make sure that the connection that you solder, does not corrode seal the connection with a high grade of silicone rubber. Use something like GE.

[Hamspiced]

Had the same issue. Heres what it was. The solution. Since i couldnt find anywhere on the net of a resolution.

There is a grene wire that is wrapped tightly in a bundle of wires that extends underneath the decorative plastic cover down to the fan temp switch up to the fuse block.

This tightly wrapped group of wires is just wrapped in high temp electrical tape but not heat shield. Its pressed between the side of the valve covers and the plastic top cover.

From 70k of vibrations from the engine the valvecover slowly wears on this green wire untill it breaks through the shielding of the wire and grounds out.

Or it just breaks the wire inside without breaking the casing.

I provided pics so you can see yourself.

But i cut the wire, jumpered it, and retaped everything. works great, light went away and overheating issue is no more.