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Discussion Starter #1
Where is the body control module located on a 2002 envoy sle? Is it under the rear driver side seat on top of the fuse box just want to make sure I'm right
Also can a faulty BCM make the Hvac system act up?
Who took my truck to a air condition and he's specialist and he recalibrated the system and then they went back off the actuators of good he said he said it's a bad BCM
 

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2002 chevy trailblazer_lt
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Where is the body control module located on a 2002 envoy sle? Is it under the rear driver side seat on top of the fuse box just want to make sure I'm right
Also can a faulty BCM make the Hvac system act up?
Who took my truck to a air condition and he's specialist and he recalibrated the system and then they went back off the actuators of good he said he said it's a bad BCM
The BCM is located in front of the rear fuseblock under the left side of the rear seats.
If it needs to be replaced with a new one it MUST be programmed to the VIN # of the truck. Cannot just grab one from the junkyard.
 

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2002 chevy trailblazer_lt
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Where is the body control module located on a 2002 envoy sle? Is it under the rear driver side seat on top of the fuse box just want to make sure I'm right
Also can a faulty BCM make the Hvac system act up?
Who took my truck to a air condition and he's specialist and he recalibrated the system and then they went back off the actuators of good he said he said it's a bad BCM
The BCM does not operate the HVAC system. The HVAC control module does that.
 

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Discussion Starter #6
Where is the body control module located on a 2002 envoy sle? Is it under the rear driver side seat on top of the fuse box just want to make sure I'm right
Also, can a faulty BCM make the HVAC system act up?
I took my truck to an air condition and he's specialist and he recalibrated the system and then they went back off the actuators are good he said he said it's a bad BCM
I'm having a problem with cold air coming out of the driver vent, I took my envoy to an AC/heat tech, and he recalibrated the system and it worked for 15 min before it stopped.
The tech thinks it may be a bad body control module affecting the HVAC system he put it on a scanner I just want to know how many and where is the BCM on the envoy 2002?
 

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2002 chevy trailblazer_lt
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The BCM IS NOT THE PROBLEM.

But you can go ahead and open that can of worms if you wish.

The trouble is most likely the drivers side temperature blend door actuator. These actuators use plastic gears inside. The plastic gets brittle when it gets old. The recalibration overloads the old plastic gears and they break or start to crack and then the output shaft slips on the gear(s).

IMG_20190319_184322.jpg
IMG_20190320_110035.jpg
 

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Discussion Starter #8
So you think the recalibration made it work for a short time?
The temp blend door actuator and defrost actuator are the same correct?
The reason Im asking is because the whole driver side is cold vent,floor and defrost while the passenger works fine.

I really appreciate your help with this
 

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So you think the recalibration made it work for a short time?
The temp blend door actuator and defrost actuator are the same correct?
The reason Im asking is because the whole driver side is cold vent,floor and defrost while the passenger works fine.

I really appreciate your help with this
Do you think I should replace both actuators?
Defrost and temp?
 

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So you think the recalibration made it work for a short time?
The temp blend door actuator and defrost actuator are the same correct?
The reason Im asking is because the whole driver side is cold vent,floor and defrost while the passenger works fine.

I really appreciate your help with this
Yes, the defrost and driver temp blend are normally the same part number.


Take a close look at the second photo. See the crack right near the metal shaft? That sort of thing can let the metal shaft that moves the door slip on the plastic gear. So sometimes it will wind up in the right orientation for a while but then later it can slip to another position that is wrong. Mine did that sort of thing for a year or more before I studied the system, took out the actuators, inspected them internally and replaced as needed.

IMPORTANT NOTE!! Inside the actuators is one small gear that only meshes with the large gear. In my first photo above it is the small blue gear. That is the position sensor for the actuator and it has to be in a very specific alignment with the final drive that moves the door. If for any reason an actuator is opened up it is imperative that the gears not be messed with unless you know how to realign them!!
 

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This is what happens during recalibration. Each truck might be just enough different in assembly that there is no known preset location for each of these doors at fully open or fully closed. To learn where the stops are the HVAC control system will run each of the actuators in each direction until it sees the gears have stopped turning. It knows they are turning or not by reading the output of that small position sensor gear on the circuit board. But if the gears are old and brittle instead of stopping at fully closed or fully open the gears break. Sometimes they lose a tooth, sometimes they crack and so on. Sometimes they can hold on just enough to get the recalibration done but then slip later and stop working right.
 

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2006 gmc envoy_denali
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The BCM IS NOT THE PROBLEM.

But you can go ahead and open that can of worms if you wish.

The trouble is most likely the drivers side temperature blend door actuator. These actuators use plastic gears inside. The plastic gets brittle when it gets old. The recalibration overloads the old plastic gears and they break or start to crack and then the output shaft slips on the gear(s).

View attachment 56546 View attachment 56547
TJ IS DEAD ON. No question about it. I had the same issue on my 2002 SLT with climate control. It’s not easy to to reach unfortunately but not that expensive either. There are also good video links and pictures here for DYI repair. Not surprised by the tech’s advice, but that is not your issue.
 
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