Question about GMC Envoy XL

1 Answer

I have an '06 GMC Envoy XL. The rear air only blues from the top vents and can only be controlled by the front control switch. Apparently the rear controls don't appear to be operational. It's a manual system, not digital. All fuses are ok and rear blower works, most of the time, on all three settings. Just can't seem to change speed, mode, or two with rear controls. How do I test the rear control module to verify its probably failure? Thank you.

Posted by on

  • Jeff Armer
    Jeff Armer Jan 12, 2019

    Or possible U code's . Do you know what those are ?
    A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The scan tool communicates with the following modules on the class 2 serial data circuit:

    • The body control module (BCM)

    • The communication interface module (OnStar®), w/UE1

    • The digital radio receiver (DRR), w/U2K

    • The driver door module (DDM)

    • The driver seat module (DSM), w/AAB

    • The DVD player

    • The electronic brake control module (EBCM)

    • The endgate module (EGM), for XUV

    • The HVAC control module

    • The HVAC control module - rear auxiliary

×

Ad

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

  • GMC Master
  • 576 Answers

The testing procedure is fairly long ,to much to post here . The first test would be to hook up a factory or some other professional type scan tool an check for DTC'S - diagnostic trouble codes .
Auxiliary HVAC Control Module
The auxiliary HVAC control module is a class 2 device that interfaces between the rear seat occupants and the auxiliary HVAC system to maintain auxiliary air temperature and auxiliary air distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all auxiliary HVAC DTCs and settings will be erased from KAM. The auxiliary HVAC control module will perform a recalibration of the electric actuators when commanded with a scan tool or if KAM is lost. This will ensure the actuators are moving with in the calibrated range. During this calibration process the auxiliary blower motor will be disabled for up to 3 minutes.

Do you know what class 2 is ? It is a serial data network for the control modules to talk to each other .

Air Distribution - Auxiliary Control
The auxiliary HVAC system provides ventilation for the rear seat occupants.
The auxiliary mode actuator shares a control circuit with the auxiliary air temperature actuator. The auxiliary mode is controlled by a rotary knob on the auxiliary HVAC control module. If change of position is required for both actuators, then the auxiliary HVAC control module positions the auxiliary air temperature actuator first. All control circuits for the auxiliary actuators are at a low voltage potential until a change of position is required. The module then applies a high voltage potential to the appropriate control circuit, which will rotate the actuator.

Air Speed - Auxiliary
There are two separate controls for the auxiliary HVAC system. There is the front auxiliary blower motor switch and the auxiliary HVAC control module. If the front auxiliary blower motor switch is in any other position than OFF or REAR, then the auxiliary air temperature actuator mimics the set passenger temperature. The auxiliary mode will mimic the primary mode. If the front auxiliary blower motor switch is in the REAR position, then the system will only function with inputs to the auxiliary HVAC control module. If the front auxiliary blower motor switch is in the OFF position, then the auxiliary HVAC control module does not respond to input. The auxiliary HVAC control module can not request A/C operation from the PCM. The rotary blower switch on the auxiliary HVAC control module provides the operator the ability to select several blower speeds. The auxiliary HVAC control module provides a pulse width modulated (PWM) signal to the auxiliary blower motor through the auxiliary blower motor speed control circuit. The auxiliary blower motor changes speed based on the received PWM signal from the auxiliary HVAC control module. Power and ground are provided to the auxiliary blower motor through the battery positive voltage and ground circuits. Power and ground are provided to the auxiliary HVAC control module by the ignition 3 voltage and the ground circuits.

Auxiliary Console Mode Actuator
The auxiliary console mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5 volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the auxiliary HVAC control module grounds one of the control circuits while providing the other with 12 volts. The control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module grounds both control circuits.

Auxiliary Mode Actuator
The auxiliary mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5 volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the auxiliary HVAC control module grounds one of the control circuits while providing the other with 12 volts. The control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module grounds both control circuits.

It's nice to know how thing's work before trying to fix it .

Posted on Jan 12, 2019

  • Jeff Armer
    Jeff Armer Jan 12, 2019

    The following DTCs are for the auxiliary HVAC door actuators:

    • B0145 is for the auxiliary mode actuator.

    • B0428 is for the auxiliary air temperature actuator.

    • B3531 is for the auxiliary console mode actuator.

  • John Doe Jan 13, 2019

    Hey Jeff, thank you. I've been out of the auto industry for 20 years. Things have changed. Unfortunately I have no access to a scan tool. Your info does help though. Guys I'm going to have to go old school and start doing some good old wire tracing, continuity testing, and voltage checks. I appreciate your assistance and thanks again.

×

Ad

6 Suggested Answers

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi there,
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this issue over the phone in a minute or two.

Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.

Here's a link to this great service

Good luck!

Posted on Jan 02, 2017

Ad
  • 63 Answers

SOURCE: 2003 Trailblazer No air from front face vents

first check to see if you have power going to the actuators when you switch the switch to it location if no power replace controller if you have power and no movement from actuators replace actuator. if actuators move remove hvac box and check for broken blend doors.

Posted on Jan 22, 2010

fphandyworks
  • 56 Answers

SOURCE: Rear heat blows cold air

one of the second heater core lines is clogged.

Posted on Jan 05, 2009

chryslertech
  • 115 Answers

SOURCE: Replacing Blower Motor Resistor

  1. Disconnect and isolate the battery negative cable.
  2. Open the glove box.
  3. Flex both sides of the glove box bin inward near the top far enough for the rubber glove box stop bumpers to clear the sides of the glove box opening, then roll the glove box downward.
  4. Reach through the glove box opening to access and disconnect the instrument panel wire harness connector for the blower motor resistor from the resistor connector receptacle (Blower Motor Resistor).
  5. Reach through the glove box opening to access and disconnect the blower motor pigtail wire connector from the resistor connector receptacle.
  6. Remove the two screws that secure the blower motor resistor to the evaporator housing.
  7. Remove the blower motor resistor from the evaporator housing.80ac4e54.gif

Posted on Mar 08, 2009

seans46
  • 161 Answers

SOURCE: 2004 Lesabre Blower Control Module Replacement - help moving DIM

First their is a blower motor resistor near the blower motor it controls and regulates the power going to the blower motor. This needs to be changed with the blower motor. If it was me and you want to fix your self with out taking to a shop I would change the blower motor and resistor. If this doest fix the problem you can return the items to your part store.One thing you can do is locate the resistor you will see the wires large ground and large power wires along with reg wires check to make sure it has power going to it on I believe 2 wires large power and small power wires if it does have power check other wires as you turn the fan high to low and see if anything. if you have power going to the resistor change them both. If this doesnt work and you still want to fix the modual should have 4 torx or 4 small metric bolts like 5.5 or 7mm remove them lift mod off. Just replacing most people do not recalibrate. At like GM they can put it on a scanner and check the operation of each part and they also reclibrate with the "Tech 2 scanner" . but first check the resistor for power if it has power change the resistor and blower motor

Posted on May 24, 2009

  • 33 Answers

SOURCE: Air doesn't come out front vents

look under your hood for any vaccuum leaks. check all rubber hoses under the hood. they should be roughly the size of your pinky.

Posted on Aug 08, 2009

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

Raido wire diagram 2002 envoy


2002 GMC Envoy Car Stereo Wiring Chart
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: The radio harness does not provide a switched power source. Run a wire to the fusebox or ignition switch harness for switched power.
Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: N/A
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

Jul 23, 2012 | 2002 GMC Envoy XL

1 Answer

The front vents in my 03' gmc envoy will not blow cool air, but all other vents work, say sides , underdash, defrosters and rear vents are working. im being told its the blend doors not opening, im...


i dont think warrenty will cover this unless you have an extended warrinty however i think your problem is with your climate control switch on the dash

Sep 14, 2011 | 2003 GMC Envoy

1 Answer

My air blows good in my vechile but the problem is that the air won't out out of my front vents. when I put the dail on the front vent it blows out on the floor. what can I do to fix my problem. I...


Could be one of two things, HVAC needs to recalibrate itself or one of the blend doors (or its actuator) is stuck. To accomplish the recalibration, set all HVAC controls and switches to their OFF or CCW positions, pull fuses # 36 and 39 in the rear fuse panel, wait about a minute then reinstall fuses. Do not touch any of the HVAC controls for 2 -3 minutes. If this does not resolve the vent issue, you will need to have the HVAC diagnosed by a technician.

Jul 11, 2011 | 2004 GMC Envoy

1 Answer

I have an 06 gmc envoy denali xl and i'm having a rear end saggin


There is a bulletin for this problem.You have to go to the dealership and have the air spring sensor calibrated.Only the dealers can do this calibration.It does not take long to calibrate a vehicle.Unless they find a different problem.Hope this helps.Good luck.

Mar 25, 2010 | 2006 GMC Envoy XL Denali

1 Answer

I have 2003 gmc envoy my front ac control does not


Need to check to see if the blower motor is running.If it is,but not threw the vents,most likely a vent door actuator motor.The actuator motor in this case would be bad,it is hard to get to,unless you are mechanically inclined,You can do it your self.If the blower motor is bad,just replace it.Check fuses first,and the blower relay.If I can help,let me know.

Aug 29, 2009 | 2003 GMC Envoy Xl

1 Answer

2003 envoy xl fan not blowing air out front vents. But air coming out back vents but its hot


sounds like you have two problems, if there is no air from front then you need to ck power to your blower motor, if no power you need to ck your blower resistor and connector, second if no cool air from rear your compressor may not be engaging, make sure you ck your fuse for the front hvac system.

Jul 29, 2009 | 2003 GMC Envoy

1 Answer

No air coming out of rear vents


check the hoses going to the rear vents.

Jul 02, 2009 | 2004 GMC Envoy

1 Answer

Electrical malfunctions in 2006 GMC Envoy XL


Check your ignition switch by checking the voltage at the fuses for affected circuts vs. other circuts that are working well...

Jun 21, 2009 | 2006 GMC Envoy Xl

1 Answer

2002 GMC Envoy xl both rear vent windows wont open


The fuse sometimes located by rear controls or could be switch faulty..Double check that!

Jun 16, 2009 | 2002 GMC Envoy XL

1 Answer

Rear heat blows cold air


one of the second heater core lines is clogged.

Jan 05, 2009 | 2004 GMC Envoy

Not finding what you are looking for?
Cars & Trucks Logo

Related Topics:

34 people viewed this question

Ask a Question

Usually answered in minutes!

Top GMC Experts

Marvin
Marvin

Level 3 Expert

83843 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22413 Answers

Jeffrey Turcotte
Jeffrey Turcotte

Level 3 Expert

8841 Answers

Are you a GMC Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...