Fan 2 Control Circuit stumped?

MANUELD1977

MEMBER
2004 CHEVROLET IMPALA
3.4L
V6
2WD
AUTOMATIC
210,403 MILES

I am getting this Fan 2 Control Circuit code even after replacing the relays the fuses even replaced whole fan assembly and it is still coming up. Code is P0481 Fan 2 Control Circuit an it's saying the fix for the code is to replace fan relay or replace fan motor relay. But it's not causing me any overheating issues and the fans kick on n off as should do. After resetting codes and starting car engine light is off if I shut it off and start it again check engine light pops back on and when I run the code scan it shows up P0481 again. Just unsure of what else it be if already replaced everything it says will fix code error but it's still showing.

Sunday, February 15th, 2026 AT 5:32 PM

2 Replies

KEN L

MASTER CERTIFIED MECHANIC
55,291 POSTS

So when you start the engine and turn on the AC does both fans come on? If not this will be the problem. Also there is a ground I would check g101 which is the top left front of the radiator support, much sure it is clean and secure.

P0481 - Fan 2 Control Circuit

Also, remove the relays again and look for overheated terminals in the fuse panel, you can tell because the plastic will be melted around them. Please let me know what you find. Ken

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Monday, February 16th, 2026 AT 8:48 AM

STEVE W.

MECHANIC
15,676 POSTS

P0481 is a high speed fan control circuit code. The PCM monitors the circuit that goes to the fan 2 and 3 relays for shorts, opens and low resistance. For testing the circuit a simple test light can show the powers and grounds. For low speed operation both fans run because power goes from relay 1 through the fan, then to relay 2 which has normally closed when off. The power then comes through the harness to the second fan and through it to ground. It effectively takes the battery voltage and makes the fans run like they were 6 volts. If that part of the circuit were the problem you would get a P0480 code as the PCM monitors relay 1 as well. In this case the other 2 relays are the monitored circuit. As you have replaced the relays with no change it likely isn't them. That leaves the wiring and the relay sockets. As you have both fans running on low G101 should be OK as it isn't monitored and the fans run. Instead the issue is likely in the dark blue wires that go to the control sides of relays 2 and 3. The system monitors both of them as a single circuit. A quick test that should work would be to unplug the coolant temperature sending unit. That should tell the PCM to turn both fans on high speed. When that happens relay 2 will switch the circuit from both fans in series for low speed to splitting them. They should then both switch to high speed as the relays switch them to individual grounds. Do you have access to a scan tool that has bidirectional control? That would make testing far easier. Without one you would need to test the resistance between the relay terminals and the PCM on the dark blue wire that connects them to pin 5 on C1at the PCM

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