Cooling fan will not turn off

[JennaBear]

Sounds like the harness, the PCM won't intermittently have issues. Check your wiring.

 

[davidr]

Sounds like the harness, the PCM won't intermittently have issues. Check your wiring.

I too have a BB tune. I also have an autocal. I reflashed back to stock and still have the same problems.

I am looking in to the other suggestions and will get back.

Jenna, I have factory harness and factory fans.

 

[JennaBear]

Have you checked all your grounds/wiring? Definitely something going on electrically.

 

[davidr]

Have you checked all your grounds/wiring? Definitely something going on electrically.

If you can provide a triage list or something, that would be great. Even better would be if anyone can plug in my issues in to alldata or similar and post the troubleshooting. I would greatly appreciate anything like that!!

 

[JennaBear]

Blue PIN 42 is grounding someplace. If you disconnect the PCM do the fans turn off? If not, it is not the PCM. If it does shut off, definitely that PIN.

Sent from an ice cream sammich.

 

[davidr]

Blue PIN 42 is grounding someplace. If you disconnect the PCM do the fans turn off? If not, it is not the PCM. If it does shut off, definitely that PIN.

Sent from an ice cream sammich.

Jenna,

I assume you mean unplug both plugs from the box (PCM) that is mounted to the firewall in the engne compartment on the driver side?

Where is pin 42? Is in the big set of plugs locked together near the PCM that has 4 separate pin sets (2 on each side)?

Also, an update. I unplugged the fans all day so they would not start. I got home, plugged them back up (I only unplugged the one on the driver side) and they started up. I then unplugged BOTH and plugged them both back in and the fans did NOT turn on... If that means anything...

Also, the knock sensor codes will pop if I drive and steer the truck to the right (for example leaving 395 on to 495 towards Tysons, since I know you know the area... Not sure it is related, but I am going to replace the sensors and harness.

 

[JennaBear]

No, the Pcm is near the battery. PIN42 is on the Pcm.

Sent from an ice cream sammich.

 

[davidr]

No, the Pcm is near the battery. PIN42 is on the Pcm.

Sent from an ice cream sammich.

Jenna - I pulled the PCM out of the truck. I looked at the wiring harness but could not see any burns, chaffing, etc. I did notice some "water damage" like residue on the face of the harness. I am not sure how to determine which set of pins it was, but it was on the lower outer harness pins. I sprayed it with some air and some water was present around the entire lower harness area.

I then took a look at the PCM itself. Again, the "blue" side and what would be the lower and outer plug section of the unit when installed, had noticeable residue around the inner walls near the bottom. There was also some standing water (4 or 5 large drops worth) that came out of the plug area when I turned it on the side. I also noticed the greenish residue on 2 pins. The 2 pins seem to be the ref. 5v pins based on a google search of a pinout. I should have counted which ones they were, but I was in a hurry and recall them being about 4 to 6 pins from the bottom. A few other pins were also a little cruddy looking, but there were the two which looked like they had been dipped in acid or something..

What I have done:

- I sprayed electical contact cleaner on the harness in question, used a toothbrush to gentle scrub the connector. Blew dry with a compressor, repeated and blew dry again. I then inspected for any particles or residue and let it sit in open air to dry some more while I moved on to the PCM.

- I sprayed the area with the greenish residue on the pins as well as the inner plug housing with electronic contact cleaner. I used a small plastic flat toothpick to gentle scrape the pins clean of the residue as well as also scraped all residue off all the other pins. I then sprayed it dry with air. I inspected. I saw some residual residue, so I repeated the process.

- I then inspected the rest of the housing, pins, plugs, etc. All looked ok.

- I allowed everything to sit and air dry for 15 minutes or so. I did not have any contact goop to put on the pins, but did not see where any was on it previously. Hopefully that is ok. I wanted to put some on there for future moisture barrier, but did not want to create any additional problems, etc...

- I reinstalled everything and checked all connections, reinstalled the battery cables and started the truck. No fans on, etc.. I let it run to normal running temps and no fan. This is a good thing!

- I then gratified my truck by re-flashing her BlackBear tune back from the stock tune.

I am taking it out today for extended trip across town. I will update everyone when I get back. In the meantime, anyone have the pinout for a PCM on a 2006 Tahoe z71?? I am almost inclined to think that the corrosion and water may have something to do with the knock sensor sporadic code I have been getting... Interested to see if knock sensors are plugged in to the PCM. I assume they due to their purpose.

Thanks!

 

[JennaBear]

On the PCM, there should be a black rubber cover, when you remove that, you will notice a bunch of wires going into different slots (PINs). Each slot has a number.

 

[Debi]

I am having the same problem with my 2005 Tahoe

UPDATES:

- Replaced all 3 relays. I tested the old relays and all seemed ok. I tested the new relays before installing, all tested good.
- Turned on the car, same results.
- I pulled the connections to the PCM and checked for burnt runs, etc. Nothing with visual inspection. I did hit them with contact cleaner before I plugged them back in.
- I pulled the wires off the ECT while truck was running. Fans continued to run. Truck threw a P0118 fault, as expected. I reset that code.
- I disconnected the large harness beside the relay housing and checked all connections visually. I hit them with contact cleaner and reinstalled.
- I pulled the ground strap at the firewall and cleaned the connection.
- Truck is NOT overheating (I replaced the radiator, thermostat and all hoses about 3 months ago)


OBSERVATIONS:
- Fans run on HIGH when car is running.
- Fans run on LOW when car is shut down.
- If I disconnect battery and reconnect, the fans shut off until I restart the vehicle. Then they turn on and back to aggrevating me.
- If I pull relay to "COOL FAN 1" both fans stop. If I plug it back in, they start back up.
- If I pull relay to "COOL FAN 2", there is no change.
- If I pull relay to "COOL FAN 3", both fans stop.
- If I disconnect the wires to the fans themselves, they obviously stop.
- Here is where it gets interesting...If I disconnect the wires to one specific fan, the fans stop. The wires I pulled are to the fan on the driver side (Black and Blue) wires.

For now, I am keeping the plug to the fan (black and blue wire set) unplugged so I can drive and not drain battery. It is cold enough and the fans don't run much in the winter, if ever.



Any ideas?