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pocomenomosso 10-20-2018 01:24 AM

Fan always on
 
P0481 code. Malfunction on high speed cooling fan control circuit

Fan comes only after I've started the car and then it stays on.

It does not come on when I turn the key to the ON position, with engine off.

Relays are fine and are not stuck.

The ECT and the IAT sensors are fine and reading rational temperatures. Engine load is OK. TPS position sensors are OK.

Using a scanner, while the car is running I can turn off the fan by the commanding the computer to turn it off. And when I command the ECM again to turn on, the fans will kick on.

So what in the world is going on here?

Maybe I will need to check the A/C stuff? I am rather jaded with the car stuff lately. I've had to trouble shoot and fix multiple problems the past 4 months and, always on weekends where I have the most work to do.

Bruce Rock 10-20-2018 09:03 AM

Re: Fan always on
 
What is the scanner you use to control fan?

far2grumpy 10-20-2018 10:59 AM

Re: Fan always on
 
[QUOTE=pocomenomosso;2284107]P0481 code. Malfunction on high speed cooling fan control circuit

Fan comes only after I've started the car and then it stays on.

It does not come on when I turn the key to the ON position, with engine off.

Relays are fine and are not stuck.

The ECT and the IAT sensors are fine and reading rational temperatures. Engine load is OK. TPS position sensors are OK.

Using a scanner, while the car is running I can turn off the fan by the commanding the computer to turn it off. And when I command the ECM again to turn on, the fans will kick on.

So what in the world is going on here?

Maybe I will need to check the A/C stuff? I am rather jaded with the car stuff lately. I've had to trouble shoot and fix multiple problems the past 4 months and, always on weekends where I have the most work to do.[/QUOTE]

I don't have experience with 2.2 but have circuit diagrams.

P0481 is set when ECM detects an open circuit (0 volts) between ECM C1-13 and COOL FAN HIGH relay contact 86.

Are you positive the fan is running high speed? You could remove COOL HIGH 40A fuse to be certain.

If fan is running LO SPEED and ECM detects P0481 condition the ECM could default to run fan LO SPEED whenever RPM is detected.

Another possibility ... AC could be running (would not explain code P0481) because: (1) AC refrigerant pressure sensor is faulty, or (2) compressor clutch is latched because HVAC is in AC mode (compressor will run but LED will not be lighted if mode switch is set to DEFROST/DEFOG or FLOOR) and fan switch is set to any speed other than OFF.

I have several diagrams ... PM email address if you'd like to have them.

Beasleylou 10-21-2018 09:27 AM

Re: Fan always on
 
Check your fan speed resistor behind driver side wheel liner.

waiter21 10-21-2018 09:52 AM

Re: Fan always on
 
Cooling fan resistor..

[url]https://www.youtube.com/watch?v=tqN1g3VPs5M[/url]

pocomenomosso 10-25-2018 03:29 AM

Re: Fan always on
 
[QUOTE=far2grumpy;2284134]
If fan is running LO SPEED and ECM detects P0481 condition the ECM could default to run fan LO SPEED whenever RPM is detected.
[/QUOTE]

Where exactly did you get this information?

(And why is it that I have not come across this in my resources? I'm frustrated that circuit and DTC descriptions that are supposed to be manufacturer's, don't give me this information!)

I'm going to check the resistor when I have the time.

If you're saying that an open in the low speed causes the ECM to command the high speed fan on then that would make sense because it's that's circuit that cuts on when I start the car. No fans run when I remove that relay and it can't be that there's an open on that circuit because I'm able to toggle it on or off with my scanner.

The p0481 is supposed to be an open in the high speed circuit. That's what has been confusing me.

I'll check out the fan resistor. I hope it's not too bad to get to.

Thanks a million, guys!

Beasleylou 10-25-2018 02:58 PM

Re: Fan always on
 
Itís easy to get to. Take off the driver side wheel liner. Just a bunch of those black plastic push button clips. No need to remove tire, headlight or anything else.

far2grumpy 10-25-2018 04:13 PM

Re: Fan always on
 
[QUOTE=pocomenomosso;2284532]Where exactly did you get this information?

(And why is it that I have not come across this in my resources? I'm frustrated that circuit and DTC descriptions that are supposed to be manufacturer's, don't give me this information!)

I'm going to check the resistor when I have the time.

If you're saying that an open in the low speed causes the ECM to command the high speed fan on then that would make sense because it's that's circuit that cuts on when I start the car. No fans run when I remove that relay and it can't be that there's an open on that circuit because I'm able to toggle it on or off with my scanner.

The p0481 is supposed to be an open in the high speed circuit. That's what has been confusing me.

I'll check out the fan resistor. I hope it's not too bad to get to.

Thanks a million, guys![/QUOTE]

You've done a great job of proving the HIGH SPEED cooling circuit is good.

Waiter21 and Beasleylou offer excellent advice pointing out cooling fan resistor is most likely suspect.

The information I posted is from GM service manual but I repeat I have no practical experience with 2.2 engine.

In a perfect world the ECM would set code P0480 (open LOW SPEED fan circuit) when resistor opens but that obviously didn't happen in this case.


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