Question about 2005 GMC Yukon Xl Denali

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2005 GMC Yukon Denali XL - Climate Control issue- Rear heat blows cold, Front heat working fine. Rear Climate Control worked fine in summer in a/c mode. Problem noticed when turning rear temperature from cold to hot â?? outside temperature 24 degrees. No difference between using driver overhead controls or rear passenger center console controls - checked fuses. Blower fan controls working fine, and floor versus roof air flow directional controls working fine. Tried removing 10 amp hvac/eacs fuse under hood and turning key on for 60 seconds as suggested by someone as a way to reset system to default settings. Nothing successful so far. Thanks

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  • 5 more comments 
  • Emmett Garlock Nov 02, 2010

    not aware of any codes, do not have capabilty to retrieve them, I hear no clicking or ticking noise in the rear

  • Emmett Garlock Nov 02, 2010

    not aware of any codes- do not have anyway to retrive them. there are no clicking or ticking noises-

  • Emmett Garlock Nov 02, 2010

    is fuse removal a known solution to this problem and if so which fuses? any on side panel, under dash or under hood?

  • Emmett Garlock Nov 03, 2010

    I'll try these steps tomorrow when its daylight. You seem to be recommending 3 solutions as follows:
    1.disconnecting battery to clear codes.
    2.or pulling fuses(which ones ? ) to reset them, or,
    3.Alternate method to clear DTC's (without scan tool) . Which do you recommend?

    Regarding 3. you say install HVAC actuator -- what is that , is it something I have removed? is it a fuse?You say connect all previously disconnected components - ? what components have you instructed me to disconnect?

    You say verify that no DTCs have set as current DTCs --- How do I do that?

    Sorry for my confusion , not a mechanic, reading your reply closely and therefore the questions.

  • Emmett Garlock Nov 03, 2010

    ok 1. I guess the pulling fuses on side panel is the recommended step at this time and no fuses under the hood are involved ( please confirm) 2. with ignition in the off position, after removing both fuses for a minimum od 10 seconds, I'm to reinstall them and then 3.start the vehicle, do not touch any controls and let it run for 40 seconds. I'm still confused on how to verify that no DTCs have set as current? 4. then turn off ignition , restart touch nothing. Please confirm I have the steps correct on the fuse pulling alternative and then I'll try it.

  • Emmett Garlock Nov 03, 2010

    ok 1. I guess the pulling fuses on side panel is the recommended step at this time and no fuses under the hood are involved ( please confirm) 2. with ignition in the off position, after removing both fuses for a minimum od 10 seconds, I'm to reinstall them and then 3.start the vehicle, do not touch any controls and let it run for 40 seconds. I'm still confused on how to verify that no DTCs have set as current? 4. then turn off ignition , restart touch nothing. Please confirm I have the steps correct on the fuse pulling alternative and then I'll try it.

  • Emmett Garlock Nov 03, 2010

    In the earlier more lenghty post describing the Alternate Method(w/o scan tool) for removing DTCs you state ---- Remove the HVAC/ECAS fuse for a minimum of 10 seconds. Install the HVAC/ECAS fuse. Start the vehicle. Wait 40 seconds for the HVAC control module to self-calibrate. ------ The HVAC/ECAS is under the hood. Should it be removed at the same time along with the two in driver side dash panel?

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Are you aware of any codes that may stored in the body control module and do you hear a clicking or ticking noise in the rear?

Posted on Nov 02, 2010

  • 6 more comments 
  • Jonathan S
    Jonathan S Nov 02, 2010

    Possibly the reason pulling the fuse did not help is that the rear HVAC may already be stuck in the default mode/settings.

  • Jonathan S
    Jonathan S Nov 02, 2010

    You may need to disconnect the battery in order to clear DTCS but am hoping pulling the fuse will reset them.

    Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

    Alternate Method (w/o Scan Tool)
    Clear all DTCs.
    Place the ignition switch to the OFF position.
    Install the HVAC actuator.
    Connect all previously disconnected components.
    Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
    Install the HVAC/ECAS fuse.
    Start the vehicle.
    Wait 40 seconds for the HVAC control module to self-calibrate.
    Verify that no DTCs have set as current DTCs.

    After you are done you need to completely start the vehicle but do not touch any of the controls.The system will going through a recalibration process and doing so will disrupt the learning and make it go back in default.

    Let me know if this helps so we can looks at other options like a possible issue with the auxillary HVAC Module

  • Jonathan S
    Jonathan S Nov 03, 2010

    The fuses are in the instrument panel on the driverside dash by the door there is an ECC fuse which is for the rear ac controls.There is also a HVAC 1 fuse in the same panel remove these 2 fuses.

  • Jonathan S
    Jonathan S Nov 03, 2010

    This is a procedure after replacing an actuator which allows the system to self recalibrate .At this point you are not replacing an actuator but the HVAC restoring process will be the same. Try removing the HVAC 1 fuse and the ECC fuse located on the driverside instrument panel. then reinstalling after a minimum of 10 sec. Then start the vehicle so the recalibration process will begin but do not touch any HVAC controls. Disconnecting the battery is the last thing you will want to do unless it becomes necessary to clear codes if a scanner is not available and removing thoses fuses does not clear dtc's. I would definitely recommend doing the fuses first.
    These are generic instructions from GM was much easier to copy and paste vs typing all information out. No problem just trying to help best I can.

  • Jonathan S
    Jonathan S Nov 03, 2010

    No underhood fuses pulled at this time. Checking for diagnostic trouble codes requires a scan tool. The diagnostics codes themselves may be the cause of incorrect operation which is why we need to get rid of them. Removing the fuses may allow them to clear and normal operation will return. If it does not that is when we would try the process again after disconnecting the battery. When the system is recalibrating you will hear clicking and blend doors moving. We need to start with this process first to see if it corrects the issue prior to moving to an HVAC module or actuator issue. Thank you for your patience.

  • Jonathan S
    Jonathan S Nov 03, 2010

    after the calibration stops then you should be able to start adjusting temperature settings and speeds

  • Jonathan S
    Jonathan S Nov 03, 2010

    Remove that one as well.This should clear the codes out of the BCM if there are any stored.

  • Matshall Cameron Jan 27, 2013

    I changed my battery on my 2006 Gmc Denali and the rear air only blows cold. I will not heat up as it had before. I am somewhat uderstanding the information posted above but would they be the same sort of issues i may have?

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