Fix Your Truck’s Electrical Headaches for Good
Is your 2007-2010 GMC Sierra Denali suffering from bizarre electrical issues? One minute the A/C works, the next it doesn’t. The power locks have a mind of their own, and you’re seeing warning lights on the dash that make no sense. As a technician with over two decades of experience, I can tell you that these frustrating, seemingly random problems often point directly to a failing Body Control Module (BCM). The BCM is the central command for your truck’s body electronics, and when it starts to go, it can create a cascade of issues. This isn’t just an annoyance; a faulty BCM can affect vehicle security and safety systems.
This replacement Body Control Module, part number 20939137, is the definitive solution. We take the guesswork and dealership hassle out of the equation. Before we ship it, we program the module to your truck’s specific Vehicle Identification Number (VIN). This ensures it communicates perfectly with your vehicle’s other systems right out of the box. You’re not just buying a part; you’re buying a reliable, pre-configured fix that restores the full functionality and comfort you expect from your Sierra Denali.
A Technician’s Notebook: The Case of the Haunted Sierra
A customer brought in his ’08 Sierra Denali, convinced it was possessed. The radio would switch off, the dome lights would flicker while driving, and the airbag light was on (DTC B1001). He’d already replaced the battery and checked the main grounds. After hooking up my scanner, I saw a dozen communication codes pointing away from the engine. In my shop, I’ve seen this exact pattern hundreds of times on these GM trucks. The BCM was failing internally, causing data corruption on the CAN bus network. We installed a VIN-programmed BCM, performed the quick ‘SDM Key Setup’ to clear the airbag light, and the truck was back to normal in under 30 minutes. It’s a classic fix for a complex-looking problem.
Is Your Sierra Denali Showing These Electrical Gremlins?
A failing BCM can manifest in numerous ways. If you’re experiencing any of the following, it’s a strong indicator that your 2007-2010 Sierra Denali Body Control Module needs replacement:
- ✔ Intermittent or non-functional HVAC and climate controls.
- ✔ Power windows, door locks, or mirrors working sporadically or not at all.
- ✔ An active airbag warning light, often with a DTC B1001 stored.
- ✔ Erratic behavior from the anti-theft system, leading to no-start or stalling conditions.
- ✔ Headlights, taillights, or interior lights staying on or not turning on.
- ✔ Wipers that won’t turn off or operate incorrectly.
- ✔ A cluster of seemingly unrelated diagnostic trouble codes (DTCs).
A Straightforward Guide to BCM Installation
One of the best parts of this solution is its simplicity. For the average DIYer, this is a quick and satisfying job that can be done with basic hand tools in your own driveway.
- Step 1: Safety First. Always disconnect the negative terminal from your vehicle’s battery before working on any electronic components.
- Step 2: Locate the BCM. On your Sierra Denali, the BCM is located under the driver’s side of the dashboard, typically to the left of the steering column. You may need to remove a lower dash panel for access.
- Step 3: Disconnect and Remove. Carefully unplug the electrical connectors from the old BCM. They have locking tabs that need to be pressed. Once disconnected, unclip or unbolt the old module from its mounting bracket.
- Step 4: Install the New Module. Snap the new, VIN-programmed BCM into the mounting bracket and securely plug in all the electrical connectors. You’ll hear a click as they lock into place.
- Step 5: Reconnect and Test. Reconnect the negative battery terminal. Start the truck and test all the functions: lights, locks, windows, HVAC, etc. Most vehicles will be fully restored at this point.
- Step 6: Final Checks. In some cases, an airbag light may remain on. This requires a ‘Setup SDM Primary Key’ procedure using a compatible high-level scan tool. A brake pedal position relearn may also be needed. See our FAQ for more details.
Guaranteed Fitment for Your GM Truck or SUV
This module is a direct replacement for part number 20939137 and other interchangeable numbers. It is compatible with a wide range of General Motors vehicles. Please verify your model and year below:
ESCALADE EXT 10 Body Control (BCM); (under steering column), ID 25835966
SIERRA 2500 PICKUP 08-11 Body Control (BCM); (under steering column)
SIERRA DENALI 2500 11 Body Control (BCM); (under steering column)
SIERRA DENALI 3500 13 Body Control (BCM); (under steering column), ID 25835966
SUBURBAN 1500 10 Body Control (BCM); (under steering column), ID 25835966
SUBURBAN 2500 10 Body Control (BCM), (under steering column)
YUKON XL 2500 09-11 Body Control (BCM); (under steering column)
ESCALADE EXT 07-09 Body Control (BCM); (under steering column)
SIERRA 3500 PICKUP 08-11 Body Control (BCM); (under steering column)
TAHOE 07 Body Control (BCM); (under steering column)
YUKON 07 Body Control (BCM); (under steering column)
ESCALADE EXT 11 Body Control (BCM); (under steering column)
YUKON XL 1500 10 Body Control (BCM); (under steering column), ID 25835966
AVALANCHE 1500 08-09 Body Control (BCM); (under steering column)
SILVERADO 1500 PICKUP 08-11 Body Control (BCM); (under steering column)
TAHOE 09 Body Control (BCM); (under steering column)
SIERRA 1500 PICKUP 10-11 Body Control (BCM); (under steering column)
SIERRA 2500 PICKUP 13 Body Control (BCM); (under steering column), ID 25835966
SILVERADO 2500 PICKUP 09-11 Body Control (BCM); (under steering column)
SUBURBAN 2500 07-09 Body Control (BCM); (under steering column)
YUKON 11 Body Control (BCM), (under steering column)
ESCALADE 11 Body Control (BCM); (under steering column)
ESCALADE ESV 11 Body Control (BCM); (under steering column)
SUBURBAN 1500 07-09 Body Control (BCM); (under steering column)
AVALANCHE 1500 07 Body Control (BCM), (under steering column)
SIERRA 3500 PICKUP 07 Body Control (BCM); new style (smooth door skin), (under steering column)
SILVERADO 3500 PICKUP 08 Body Control (BCM), (under steering column)
TAHOE 10 Body Control (BCM); (under steering column), ID 25835966
YUKON 08 Body Control (BCM), (under steering column)
YUKON 09 Body Control (BCM); (under steering column)
SIERRA 3500 PICKUP 13 Body Control (BCM); (under steering column), ID 25835966
SIERRA DENALI 2500 13 Body Control (BCM); (under steering column), ID 25835966
SILVERADO 1500 PICKUP 07 Body Control (BCM); new style (smooth door skin), (under steering column)
SILVERADO 3500 PICKUP 09-11 Body Control (BCM); (under steering column)
SILVERADO 3500 PICKUP 13 Body Control (BCM); (under steering column), ID 25835966
TAHOE 08 Body Control (BCM)
YUKON XL 2500 07-08 Body Control (BCM), (under steering column)
SIERRA DENALI 07 Body Control (BCM); new style (smooth door skin), (under steering column)
SIERRA DENALI 1500 11 Body Control (BCM); (under steering column)
SILVERADO 2500 PICKUP 13 Body Control (BCM); (under steering column), ID 25835966
YUKON 10 Body Control (BCM); (under steering column), ID 25835966
YUKON XL 1500 07-09 Body Control (BCM), (under steering column)
YUKON XL 1500 11 Body Control (BCM); (under steering column)
AVALANCHE 1500 10 Body Control (BCM); (under steering column), ID 25835966
SIERRA 2500 PICKUP 07 Body Control (BCM); new style (smooth door skin), (under steering column)
ESCALADE 07-09 Body Control (BCM); (under steering column)
SIERRA 1500 PICKUP 07 Body Control (BCM); new style (smooth door skin), (under steering column)
SIERRA 1500 PICKUP 09 Body Control (BCM), (under steering column)
SIERRA DENALI 3500 11 Body Control (BCM); (under steering column)
SUBURBAN 2500 11 Body Control (BCM); (under steering column)
ESCALADE ESV 10 Body Control (BCM); (under steering column), ID 25835966
SIERRA 1500 PICKUP 08 Body Control (BCM); (under steering column)
SIERRA DENALI 08-10 Body Control (BCM); (under steering column)
SUBURBAN 1500 11 Body Control (BCM); (under steering column)
ESCALADE 10 Body Control (BCM); (under steering column), ID 25835966
SILVERADO 2500 PICKUP 07 Body Control (BCM); new style (smooth door skin), under steering column)
SILVERADO 2500 PICKUP 08 Body Control (BCM), (under steering column)
SILVERADO 3500 PICKUP 07 Body Control (BCM); new style (smooth door skin), (under steering column)
AVALANCHE 1500 11 Body Control (BCM)
TAHOE 11 Body Control (BCM); (under steering column)
Frequently Asked Questions
Frequently Asked Questions
Why is VIN programming so important?
VIN programming loads your vehicle’s specific software and configurations onto the BCM. This ensures all the features your truck was built with (like power seats, specific lighting, security options) work correctly. A non-programmed module from a junkyard or generic seller will cause conflicts and won’t function properly.
Do I need a mechanic to install this?
For most people, no. The physical installation is a simple plug-and-play process that takes just a few minutes. However, if your airbag light remains on after install, you will need a professional-grade scan tool (or a visit to a shop) to perform the ‘Setup SDM Primary Key’ procedure.
What if my airbag light is on after installing the new BCM?
This is normal in some cases. The BCM and the airbag system (SDM) need to be electronically re-synced. This is done with a scan tool function called ‘Setup SDM Primary Key in BCM’. It’s a quick procedure for any professional technician.
Is there a core charge or do I need to send my old part back?
No. There is no core charge for this module. You can keep your old part, which saves you the time and expense of return shipping.
Will this fix my check engine light?
Generally, no. The BCM controls body functions, while the Powertrain Control Module (PCM) or Engine Control Module (ECM) manages the engine and transmission. A check engine light is typically related to the PCM/ECM. However, a BCM can sometimes cause security-related starting or stalling issues that may be confused with an engine problem.