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2006 Corvette Fan stuck on

 
Old 05-23-2019, 09:04 PM
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Default 2006 Corvette Fan stuck on

Hi All,

Having an issue with a buddies 2006 supercharged vette that he bought. Long story short - the original owner told him the fan module was fried and had an aftermarket one wired up. We don't like the aftermarket one because it is sloppy and don't feel it cools as good. He would like to stay with the factory setup and so we are investigating the issue.

So here is what happens when he put in a used module:
  • Ignition on, key off I try and command the fan on with hp tuners = nothing
  • Ignition on, key on, fan comes on instantly on cold start up at full blast (AC not on).
    • Turn the ignition off and the fans remain on for a 300second run cycle.
    • IF I try and command the fans off any any time with the engine running or during the cool down cycle with hp tuners I get no response.
So in other words, the car is ignoring my pcm commands from hp tuners in the specialty tab using just the VCM

For ***** and giggles we installed the previous controller module that the vette came with and the results are exactly the same.

Now, he has eliminated the plug and hard wired the wires from the pcm / power / ground as the hardness before the fan module (up by the subframe) is known to go bad, so that is also ruled out.

Looking at the tune which I am posting here I can tell the following:
  • The fans are set to come on at startup only after the car hits 168.8*F and only at 11%. Yet, at startup and well below this temperature they are on a full blast?
  • output control vs state is all set to "1" - I don't know what this function is or what those numbers mean. I thought I saw this tune as being stock as far as the fan settings go, but maybe I am missing something somewhere else? I am not over familiar with the vette tunes so it is possible I am over looking something when trying to diagnose this.

Other thoughts:
  • We thought maybe it was a PCM issue - but clearly the PCM is needed to command the fans on? But also how is it ignoring direct commands from Hp Tuners to turn on and off?
  • We thought maybe it is the coolant sensor, but it is reading the coolant temp fine
  • We thought maybe he got a faulty controller, but what are the odds both are bad and display the same symptoms? Usually when these are bad the fan just doesnt work?

We are both stumped at what to look at to diagnose. Obviously the fan works when plugged in, but not properly and not as commanded. All the issues we have read deal with the control module not working and causing the fans not to work.

Tune attached - thanks to anyone who can help out!
Attached Files
File Type: hpt
new vette tune - Copy.hpt (690.4 KB, 1 views)
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Old 05-23-2019, 09:25 PM
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It could just be a bad PCM, and always was since the issue started.
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Old 05-23-2019, 10:04 PM
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The thing is, nothing else is wrong with the PCM. We thought about the PCM being bad, but seldom have I heard that just one system has an issue within the PCM when it goes bad.
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Old 05-24-2019, 08:15 AM
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Fan driver within the ECU could be shot. Have you checked it's output with a meter or scope to see if it is locked on solid? I'm not sure of the wiring of this setup, but if it is low side drive (ground signal) to the fan module, the harness could also be shorted to ground, commanding the fan to run full tilt.
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Old 05-24-2019, 01:48 PM
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Also a thought we had- except when you turn the vette off you can hear the fan step down in power for the 300 second run
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Old 05-26-2019, 02:07 PM
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Any other thoughts? We are still stumped
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Old 05-30-2019, 01:02 PM
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A/C pressure also commands the fans. Look at the data and see what the a/c pressure shows on startup. Could be something funky there commanding the fan on before it should.


Also try the relays, one could be stuck or sticking. Move them around or swap them with other relays in the fuse relay box and see if an of the activity changes, even on other parts of the car since you could be potentially putting a funky relay on another system when you move them around.
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Old 05-30-2019, 10:01 PM
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Where is the relays? I haven’t been able to find them for the fans in this car? It was one of the first things I looked for, but nothing was labeled as a fan relay? My buddy said he believes it is all built into the controller?

Good suggestion on the AC- looks like the previous owner had all the dtc’s shut off minus P0645 - we are going to purchase credits tomorrow and try and flip that code off and see if it works. I hate to have him pay $100 usd with the amount of uncertainty we have. But we strongly believe it is a tune issue
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Old 05-31-2019, 07:42 AM
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On the 2006 Z06 the fan relay is located in the fuse box under the hood on the passenger side. I think they are called cooling fans on the Z06 it is circuit #25. 60amp relay.
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Old 05-31-2019, 12:57 PM
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Sorry my mistake. That car has a solid state control unit for the fan that is controlled by the PCM.
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Old 05-31-2019, 12:58 PM
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Originally Posted by Double06 View Post
On the 2006 Z06 the fan relay is located in the fuse box under the hood on the passenger side. I think they are called cooling fans on the Z06 it is circuit #25. 60amp relay.
I looked up the wiring diagram in all data, that is a fuse. It is #25 and it is a 60 amp but again it's a fuse. There is no relay.
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