Restore Your Truck’s Electrical System with a Pre-Programmed BCM
If you’re dealing with bizarre electrical issues in your 2007-2011 Sierra 3500, a failing Body Control Module (BCM) is often the culprit. As the central command for your truck’s body electronics, a faulty BCM can cause a cascade of frustrating problems, from non-functional power windows to a no-start condition. This replacement module, equivalent to GM part number 20939138, is the definitive solution. We utilize a professional cloning service to transfer your vehicle’s original data to this unit, ensuring a true plug-and-play installation without any expensive trips to the dealership for programming.
A Technician’s Notebook: The Grounding Gremlin
I once had a 2009 Silverado 2500 in my bay—same platform as your Sierra—with the strangest symptoms. The radio would cut out, the dash lights would flicker, and sometimes it wouldn’t start. The owner had already replaced the battery and alternator. A scan showed a dozen intermittent communication codes. Before condemning the BCM, I went straight to the main BCM ground point under the driver’s side A-pillar kick panel. Sure enough, it was loose and corroded. After cleaning and tightening the ground, half the problems vanished, but the BCM had already suffered internal damage from the erratic voltage. A new cloned 2007-2011 Sierra 3500 BCM and a solid ground fixed it for good. Always check your grounds during the swap!
Is Your Sierra 3500 Showing These Electrical Gremlins?
A failing BCM doesn’t always throw a check engine light. Instead, it creates a host of hard-to-diagnose issues. Here’s what to look for:
- ✔ Intermittent or non-working HVAC controls and blower motor.
- ✔ Power windows, door locks, or interior/exterior lights behaving erratically or not at all.
- ✔ The security or anti-theft system light is on, preventing the engine from starting.
- ✔ An airbag warning light on the dash, often with a DTC like B1001 (Setup SDM Primary Key in BCM).
- ✔ Wipers that turn on by themselves or won’t shut off.
- ✔ Communication errors with other modules, leading to various performance problems.
Your 5-Minute BCM Installation Guide
Getting your truck back to normal is a straightforward job you can do in your driveway. This 2007-2011 Sierra 3500 BCM is designed for a direct fit.
- Safety First: Always disconnect the negative terminal from your truck’s battery before working on any electronics.
- Locate the Module: The BCM is typically found under the driver’s side dashboard, to the left of the steering column. It’s a black box with several large multi-pin connectors.
- Swap the Connectors: Carefully release the locking tabs on each electrical connector and unplug them from your old BCM. Plug them securely into your new module. The connectors are keyed, so they only fit one way.
- Mount the New BCM: Secure the new module in the mounting bracket.
- Power Up: Reconnect the negative battery terminal. Start the truck and test all functions—lights, windows, wipers, and HVAC.
- Post-Install Checks: In some cases, an airbag light may remain. This requires a professional scan tool to perform the ‘Setup SDM Primary Key in BCM’ function. A brake pedal position relearn might also be needed.
Confirmed Fitment for Your GM Truck
This BCM is a direct replacement for part number 20939138 and other interchangeable numbers, ensuring compatibility with a wide range of GM trucks and SUVs. While this page focuses on the 2007-2011 Sierra 3500 BCM, please verify your part number and check the list below.
ESCALADE & ESV & EXT 07-11
SIERRA 1500 PICKUP 07-11
SIERRA 2500 PICKUP 07-11
SIERRA 3500 PICKUP 07-11
SIERRA DENALI 07-11
SILVERADO 1500 PICKUP 07-11
SILVERADO 2500 PICKUP 07-11
SILVERADO 3500 PICKUP 07-11
SUBURBAN 1500 07-11
SUBURBAN 2500 07-11
TAHOE 07-11
YUKON & YUKON XL 07-11
Note: For 2007 models, this fits the New Body Style (smooth door skin) only.
Frequently Asked Questions
What is a Cloning Service?
Cloning is a service where we transfer the critical vehicle-specific data (including VIN, mileage, and key information) from your original BCM to the replacement unit. This makes the new module a perfect electronic match for your truck, eliminating the need for dealer programming and ensuring all systems work correctly upon installation.
Do I need to send my original BCM to you?
Yes, for our cloning service, you will need to send us your original module. We perform the data transfer and then ship both your original and the newly programmed replacement back to you. There is no core charge, and you get to keep your old part.
What happens if the airbag light stays on after I install the new BCM?
This is a known GM security procedure. If the airbag light is on, it means the new BCM needs to be electronically ‘introduced’ to the airbag system’s computer (SDM). A mechanic with a bi-directional scan tool will need to perform the ‘Setup SDM Primary Key in BCM’ procedure to sync the modules and clear the light.
Is this a difficult part for a DIYer to replace?
Not at all. The physical swap is one of the easier electronic repairs. It’s located under the dash and usually held in by simple clips or a couple of small bolts. The entire process typically takes less than 15 minutes with basic hand tools.
Will this fix my intermittent no-start problem?
It’s a very strong possibility. The BCM controls the Passlock/Passkey anti-theft system. When the BCM fails, it can mistakenly think the truck is being stolen and prevent it from starting. If your security light is flashing during a no-start event, the BCM is a primary suspect.