Head scratcher for the gurus.....

[JJFlash]

Hello all,



Here at work, we have a 2005 2500 4X4 quad-cab short bed.



Since it was new, it always had a CEL with the code for "fan clutch".



We had the fan clutch replaced twice, but the light still comes on.



We have cleared the codes several times, but it STILL comes back.



Neither the dealers, nor our mechanics, can figure out why the code is still there.



Otherwise, the truck runs great, which is why folks have simply been ignoring the light.





Any ideas??

 

[Prairie Dog]

My guess is the wire that runs up the back of the radiator to the clutch has been damaged. This was a common issue back then and I can't imagine any experienced dealer mechanic not knowing about it.
If you lay under the truck and look up behind the radiator, you'll see the tube that carries the wires. Sometimes they weren't routed correctly or just came loose and got damaged.

 

[cerberusiam]

When the clutch gets replaced the harness gets replaced so the wires from the bottom of the shroud will be good. The problem has to be in the chassis harness or maybe FCM, assuming the new clutch s good.



Check the harness plug and make sure there is continuity thru all the pins. Sometimes the receptacles expand too much and the pin won't make contact.



The harder problem to find without swapping parts is a weak relay in the FCM. THAT will confound almost and diagnostic unless your down to testing actual voltages and reistance on each circuit.



The big question is whether the fan is working correctly or it is just a nuisance code.

 

[JJFlash]

Fan is working correctly.



Thanks for the help guys!



I don't know why the CEL bugs me... . It doesn't seem to bug the various drivers.