I have a 2006 chevy Silverado Z71, last week my cooling fans decided to start running after the truck has been turned off. I know they will come on if the motor is overheated even if the truck is off but the truck is never overheated and they never turn off. They will continue to run until the battery is dead.
I have changed the temp sensor and checked all 3 relays and everything looks great. Anyone have some input on what might be going on?

 

if your fans relays are breaking ground, you can have a split back ground wire touching frame somewhere or motor where it has rubbed and come in contact making ground which in turn will never turn off.....so check all your ground wires in the fan harness and make sure they are not rubbing and coming in contact with metal

 

I know if the motor is running there are 3 hot contacts and 1 grounded. while the motor isn't running therre are 2 grounds and 2 hot.

 

I cleaned the ground connection for the fans and checked the rest of the wires as best as I could and found nothing. Last night it threw a engine misfire detected, knock sensor code, fan relay switch code and was running terrible. I was also getting a blueish white smoke from the exhaust pipe and an occasional backfire. then all of the sudden the codes went away, the smoke diappeared and it started running fine again.

 

My truck has a done this a few times, I had to tap the relays a couple times and it turned off.

 

I have changed the knock sensors, changed sparkplugs, changed relays, I am still getting a misfire code and a fan circuit relay control error code. I am completely lost at this point. I am looking at buying a pcm from a 2wd Avalanche 2006 model. Does anyone know if these two pcms are interchangeable?

 

Sounds like you have a wire harness that is chafing somewhere and shorting the fan control circuts which will cause the fans to stay on all of the time, also in the same harness the coil, injector, and knock sensors are all in the same harness and if shorted to ground will cause all of the codes that you are setting!!! Sounds to me like it is time to start checking wiring!!!!

 

The PCM is interchangeable but it will not start you truck until programmed.

 

That's the thing, its not always running, when I start the truck they turn off unless I turn the ac on. then they will turn back on after the truck is off. If it was a grounded wire I thought they would run all the time regardless if the switch is on or not.

 

about 8 pins on the end of the blue connector were corroded. Got some contact cleaner from radio shack and gently cleaned it with a wire brush, seems to be running fine now and the fans have turned off. I'm still getting a little smoke from the exhaust, probably because I gutted the cats yesterday, but I'm going to run some berryman's through it and see if that helps.