If you’re tired of chasing down bizarre electrical problems in your 2007-2011 GMC Sierra 3500, you’ve come to the right place. A failing Body Control Module (BCM) is the central nervous system for your truck’s comfort and convenience features, and when it goes bad, it can cause a cascade of frustrating issues. This OEM-quality Body Control Module, part number 20939137, is the definitive solution, arriving expertly programmed to your truck’s specific VIN. This means no expensive trips to the dealership for programming—it’s a true plug-and-play fix that gets you back on the road with confidence.
As a technician, I’ve seen firsthand how a faulty Sierra 3500 BCM can make a perfectly good truck feel unreliable. From intermittent power windows to a dashboard lit up with warning lights, the symptoms can be confusing. Our module restores the precise factory control over your vehicle’s body electronics, ensuring everything from your headlights to your HVAC system works exactly as it should. Stop guessing and replace the component that is most likely the root cause of the electrical chaos.
Case Study: The Ghost in the Machine
A customer brought in his ’09 Sierra 2500 with a laundry list of complaints: the radio would cut out, the dome light would flicker, and sometimes the power locks wouldn’t respond. He’d already replaced the battery and checked the alternator. His scan tool showed a few intermittent communication codes. My first step, always, is to check the main ground points, especially the one under the driver’s side door sill plate, as corrosion there is common. In his case, the grounds were solid. We swapped in one of our pre-programmed BCMs, and within minutes, every single issue was resolved. It’s a powerful reminder that while you should always check the basics, a faulty Sierra 3500 BCM is often the central culprit for these widespread electronic failures.
Is Your Sierra Showing These Electrical Faults?
- ✔ Intermittent or non-working power windows, door locks, or mirrors.
- ✔ HVAC blower motor or climate controls behaving erratically.
- ✔ Headlights, taillights, or interior lights flickering, staying on, or not working at all.
- ✔ An active airbag warning light, often with a DTC B1001 (Setup SDM Primary Key in BCM).
- ✔ Vehicle security system malfunctions, causing no-start or stalling conditions.
- ✔ Unpredictable windshield wiper operation.
- ✔ A variety of communication-related Diagnostic Trouble Codes (DTCs).
A Straightforward Guide to BCM Installation
- ✔ Safety First: Always disconnect the negative terminal from your truck’s battery before beginning any electrical work.
- ✔ Locate the Module: The BCM is typically located under the driver’s side of the dashboard, near the steering column. You may need to remove a lower dash panel for access.
- ✔ Disconnect and Remove: Carefully unplug the electrical connectors from the old BCM. They have locking tabs that need to be depressed. Once disconnected, unclip or unbolt the old module from its mounting bracket.
- ✔ Install the New BCM: Mount your new, pre-programmed BCM and securely plug in all the electrical connectors. You’ll hear a click as they lock into place.
- ✔ Reconnect and Test: Reconnect the battery terminal. Start the truck and test all body functions—lights, locks, windows, wipers, and HVAC—to confirm the repair.
- ✔ Post-Install Checks: In some cases, an airbag light may persist. This requires a professional scan tool to perform the ‘Setup SDM Primary Key in BCM’ function. A Brake Pedal Position relearn may also be needed.
Verified Vehicle Compatibility
This module is a direct replacement for part number 20939137 and other interchangeable numbers across a wide range of GM trucks and SUVs. While this page is focused on the Sierra 3500 BCM, it also fits the following models. Always verify your part number for a perfect match.
- GMC Sierra / Denali (1500, 2500, 3500): 2007-2013
- Chevrolet Silverado (1500, 2500, 3500): 2007-2013
- Chevrolet Avalanche / Suburban / Tahoe: 2007-2013
- GMC Yukon / Yukon XL: 2007-2013
- Cadillac Escalade / ESV / EXT: 2007-2013
Frequently Asked Questions
Do I need to program this BCM at the dealership?
No. We program the module to your vehicle’s VIN before shipping. It arrives ready for immediate installation, saving you time and money.
What tools are required for installation?
Basic hand tools are all that’s needed for the physical replacement, typically a socket set and a trim removal tool for the dash panel. No special programming tools are required unless an airbag light needs to be cleared post-installation.
Will this fix my airbag light with code B1001?
Replacing the BCM is the correct first step. However, after installation, you may need a scan tool with bidirectional controls to perform the ‘Setup SDM Primary Key in BCM’ procedure to sync the new module with the airbag system and clear the light.
Is there a core charge for my old part?
Absolutely not. There is no core charge on this module. You can keep your old part without any hassle.
How can I be sure the BCM is the problem?
While the only way to be 100% certain is with advanced diagnostics, a failing BCM is the most common cause when you experience multiple, unrelated electrical issues simultaneously, such as problems with lights, locks, and windows.
What does ‘new style (smooth door skin)’ mean in the fitment data?
For the 2007 model year, GM produced two body styles. The ‘new style’ (GMT900 platform) has a smooth, modern-looking door skin without a separate plastic molding strip. This BCM fits that new body style for 2007 models.