Restore Full Command of Your Sierra’s Electronics
Are you tired of battling unpredictable electrical problems in your 2007-2011 GMC Sierra 3500? A failing Body Control Module (BCM) is often the culprit behind a frustrating array of issues, from a dead HVAC system on a hot day to power windows that have a mind of their own. This replacement BCM, corresponding to part number 20939137, is the definitive solution to restore your truck’s reliability and functionality. As the nerve center for your vehicle’s body accessories, a healthy BCM is essential for proper operation.
We take the guesswork and dealership hassle out of the repair with our professional Cloning Service. Simply send us your original module, and we’ll transfer its exact vehicle-specific data to this replacement unit. This process ensures that all your truck’s original settings and security information are preserved, making the installation a true plug-and-play experience. You get a fully functional module without the need for expensive and time-consuming dealer recalibration.
A Technician’s Notebook: The Intermittent Gremlin
I had a 2009 Sierra 2500HD in the shop that was driving its owner crazy. The radio would cut out, the driver’s side power window would work one day and not the next, and the airbag light was on with a B1001 code. The owner had already replaced the battery and checked the main grounds. After hooking up my scanner, I saw multiple communication loss codes with various modules. In my 20+ years of experience, this pattern almost always points back to a failing BCM. The internal circuits fracture over time from heat and vibration, causing these intermittent open circuits. We installed a cloned BCM, and every single issue was resolved instantly. It’s a classic failure on these GM trucks.
Is Your Sierra Exhibiting These Telltale BCM Failure Signs?
A faulty BCM can manifest in numerous ways. If you’re experiencing any of the following, it’s a strong indicator that your module needs replacement:
- ✔ The HVAC blower motor works intermittently or not at all.
- ✔ An active airbag warning light, often accompanied by Diagnostic Trouble Code (DTC) B1001.
- ✔ Power windows, door locks, or exterior lights behaving erratically or failing completely.
- ✔ The anti-theft or security system preventing the truck from starting.
- ✔ Strange electrical behavior like flickering dash lights or gauges dropping out.
- ✔ A cluster of communication codes (U-codes) stored in the system.
Your 5-Minute BCM Installation Guide
Replacing the Sierra 3500 Body Control Module is a straightforward job that most DIYers can handle in their own driveway. Follow these steps for a smooth installation:
- Safety First: Always disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the BCM: On most GM trucks of this era, the BCM is located under the driver’s side of the dashboard, to the left of the steering column. It’s a black box with several large electrical connectors.
- Remove the Connectors: Carefully depress the locking tabs on each wiring harness connector and pull them straight out from the module. They are color-coded, making reinstallation easy.
- Swap the Modules: Unclip or unbolt the old BCM from its mounting bracket and remove it. Install your newly cloned BCM in its place.
- Reconnect and Test: Plug the wiring harnesses back into the correct ports on the new BCM. Reconnect the battery terminal and start the vehicle. Test all functions like lights, windows, locks, and the HVAC system to confirm the repair.
Post-Installation Note: In some cases, if the airbag light was on, it may remain on after the swap. This requires a professional scan tool to perform the ‘Setup SDM Primary Key in BCM’ procedure to sync the modules. A brake pedal position relearn may also be necessary on certain models.
Verified Fitment for Your GM Truck or SUV
This module is a direct replacement for part number 20939137 and other interchangeable numbers across a wide range of General Motors vehicles. While this page focuses on the Sierra 3500 Body Control Module for 2007-2011 models, it also fits:
CHEVROLET SILVERADO 1500/2500/3500 (2007-2013)
CHEVROLET SUBURBAN 1500/2500 (2007-2011)
CHEVROLET TAHOE (2007-2011)
GMC SIERRA 1500/2500/3500 & DENALI (2007-2013)
GMC YUKON & YUKON XL (2007-2011)
CADILLAC ESCALADE, ESV, EXT (2007-2011)
Always verify your part number or consult the detailed fitment list to ensure compatibility.
Frequently Asked Questions
What exactly is the Cloning Service?
Cloning is a process where we transfer the complete software and vehicle-specific data—including the VIN, security keys, and option configurations—from your original BCM to the replacement unit. This makes the new module an exact electronic copy of the old one, ensuring it works perfectly in your truck without any additional programming.
Do I need to go to a dealership after installing this part?
No. Our Cloning Service completely eliminates the need for dealer programming, which can be costly and time-consuming. The module will arrive ready for plug-and-play installation.
Why is my airbag light still on after installation?
If the airbag light persists, it’s because the new BCM needs to be electronically ‘introduced’ to the vehicle’s Sensing and Diagnostic Module (SDM). This is a simple security sync called ‘Setup SDM Primary Key in BCM’ that must be done with a bi-directional scan tool. Most professional repair shops can perform this procedure quickly.
What happens to my original module?
Your original module is always returned to you along with the newly cloned replacement. We do not require a core and believe you should keep your original parts.
Is this a difficult part to install myself?
Not at all. For most owners with basic tools, this is a very simple repair. The BCM is easily accessible under the dashboard, and the entire process typically takes less than 15 minutes.