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Old 04-15-2017, 04:17 PM   #1
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i keep getting p0481 engine code control fan 2 circuit mafuntion both my fans work car isnt overheating no symptoms really i cleaned harness connectors and reattached, changed 3 fan relays 1,2,3 checked fuses theyre all good,im at my witts end.wasgoona try to replace coolent temp sensor but i have no symptoms of a bad one.and no symptoms of a bad pcm car starts right up.any other suggestions havnt check to see if their is a short in wiring i dont have a tester for that yet. i have a 04 impala 3800.
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Old 04-15-2017, 04:19 PM   #2
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Do you use a fan override?
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Old 04-15-2017, 04:20 PM   #3
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Do you use a fan override?
im sorry not really sure i just know we checked the fans both working like it should
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Old 04-15-2017, 10:55 PM   #4
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Both fans may be running but are they running at the correct speed?

I believe that those relays cause both fans to run at low speed, in series, and at high speed, in parallel, depending on coolant temp....
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Old 04-15-2017, 11:02 PM   #5
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Both fans may be running but are they running at the correct speed?

I believe that those relays cause both fans to run at low speed, in series, and at high speed, in parallel, depending on coolant temp....
yes pretty sure they are, heated engine up to the half mark which is 212 degrees and both fans were running high speed they dont go on till its gets a certain temp
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Old 04-15-2017, 11:05 PM   #6
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i was thinking of replacing the coolent control sensor for shitzz and giggles to eliminate that as i said though it doesnt overheat or anything like that but could it still be that even though it everything seems normal
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Old 04-16-2017, 12:03 AM   #7
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Based on the information on hand, I don't see a benefit to replacing the coolant temp sensor. Essentially, that code comes about when the circuits for the fans are not behaving as expected based on what the computer is commanding.

That was the reason I was asking about a fan override. If the computer detects the fans are forced on when the key gets turned on, it can throw this code, which is why I asked.
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Old 04-16-2017, 10:20 AM   #8
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yes pretty sure they are, heated engine up to the half mark which is 212 degrees and both fans were running high speed they dont go on till its gets a certain temp


At 212, they are running at low speed......they will not run at high speed until the temp gets into the 220'* or so.....so you don't know if they are running at high speed until it reaches that higher temp....you can accomplish this by blocking air flow to the radiator and then increase the rpm'* in park to 2000.....when the temp gage gets to 220-230, you should see a change in fan speed to high.....

Another way to prove they are in low speed is, disconnect the harness from one fan....in low speed they are connected in series so if you disconnect one, the other will stop also......if you disconnect one and the other keeps running, you are in high speed, which it should not be, at a lower temp.......
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