The notorious P0495 SES

dfc739

Original poster
Member
Jul 29, 2012
170
Des Moines, IA
I was driving up to South Dakota when I had P0495 "Cooling Fan High Speed" pop up. I've read some other threads that all point to the fan clutch but my symptoms don't match those of others. I do not have the loud roar typical of the failing fan clutch and I can spin the fan pretty easily by hand when it's off. I was also getting 15 mpg, which I consider acceptable for driving 75 mph into strong wind. I've never replaced my fan clutch and I've put about 60k miles on it with no other problems from the fan clutch.

I was fighting a stiff headwind (25-30 mph) for about four hours when the code turned on. I haven't cleared the code yet and I want to see if it goes away on it's own since I'm no longer fighting the wind. Has anyone ever heard of a strong headwind causing the cooling fan to turn fast enough to cause this code? Or should I order a new fan clutch and plan for its inevitable demise? Does anyone know if we can monitor commanded fan speed vs. actual fan speed with Torque?
 
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Member
Aug 25, 2012
955
I have never heard of wind causing the fan to blow fast. When you say it is easy to spin the fan when off, how easy? Like if you spin it and let it go, does it keep spinning or stop immediately. With the belt on the water pump pulley the fan should be hard to spin by hand. It should move some when you spin it by hand but have a good amount of pressure to it and when you let go of it it when you spin it, it should stop almost immediately. If you want something risky, you can get a nice thick glove or towel and attempt to stop the fan by hand. If it is operating properly, the fan should be able to get stopped when the engine is cooler. If you cannot stop it then you have a bad clutch.
 

bobdec

Member
Apr 19, 2013
233
P0495 on a '04 says fan was turning greater than 1600 RPM when not commanded on, conditions are engine RPM greater than 1800 w/o PCM activating he fan clutch. I have never been able to find actual or commanded fan speed PID's to enter into in Torque (or anywhere) the actual fan speed is RPM, but the commanded speed is an estimation, as the fan clutch duty cycle percentage varies as well as RPM. EG a fan clutch activated 50% of the time for an engine RPM of 2000 should be XXX RPM. Where a clutch activated 2% of the time for the same RPM would be YYY. Factor in wind from the grill, maybe a loose clutch could go over the speed ??? If it were mine I'd reset the DTC and watch it for a while. If clutch is loose then you should see under speed P0483's or temp problems... They messed with fan DTC's almost every couple of years trying to fix false indications till '08 when they gave up and went mechanical. IMO they saw product end of life coming and slapped in some old school fans to get GM through the'08 recession w/o committing any more engineering resources to a dead horse.
 

dfc739

Original poster
Member
Jul 29, 2012
170
Des Moines, IA
Short update: the SES turned off by itself yesterday. I drove it several times today and it did not come back on. Maybe it was a fluke, maybe not. I'll update if it turns back on.
 

IllogicTC

Member
Dec 30, 2013
3,452
dfc739 said:
Short update: the SES turned off by itself yesterday. I drove it several times today and it did not come back on. Maybe it was a fluke, maybe not. I'll update if it turns back on.
Driving into the wind all day, it very well may have set a false code. On the bright side, that sounds like your heat exchangers are still breathing easy.
 

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