Are you chasing electrical gremlins in your GMC Envoy, Trailblazer, or another GM SUV? One minute the power windows work, the next they don’t. The radio acts possessed, or worse, the vehicle won’t start. As a technician with over two decades of experience, I’ve seen these exact issues hundreds of times, and the culprit is almost always a failing Body Control Module (BCM). This isn’t just a fuse box; it’s the central nervous system for your vehicle’s body electronics, and when it goes bad, it creates chaos. This is the definitive solution to restore order.
This listing is for a replacement BCM, part number 15787809, that solves these problems without a costly trip to the dealership. We utilize a professional Cloning Service. You simply send us your original BCM, and we transfer its exact data—including VIN, mileage, and key programming—to this replacement unit. The result? A module that is truly plug-and-play, arriving at your door ready for installation. We handle all the complex programming so you don’t have to.
A Technician’s Notebook
I remember a 2006 Trailblazer that came into the shop with a complaint of intermittent no-start and a battery that would drain overnight. The owner had already replaced the battery and alternator. After checking for parasitic draws, I noticed the draw was coming from the BCM circuit. The module wasn’t ‘going to sleep’ properly, keeping other systems awake. A quick scan showed several U-codes (communication errors). Swapping in a cloned BCM fixed the draw and the no-start condition instantly. These symptoms are classic for a failing 2005-2006 Envoy XL BCM and its platform-mates.
Is Your SUV Showing These Symptoms?
- âś” Erratic or non-functional power windows, door locks, and mirrors.
- âś” Interior or exterior lights staying on or not working at all.
- âś” Key fob remote not responding or working intermittently.
- âś” The security light is on, preventing the engine from starting.
- âś” Unexplained battery drain that kills the battery overnight.
- âś” Warning lights on the dash (like ABS or Airbag) appearing for no reason.
- âś” Diagnostic trouble codes (DTCs) related to communication loss (U-codes) or BCM internal faults.
A Straightforward Guide to BCM Replacement
- âś” Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- âś” Locate the BCM: On these GM SUVs, the BCM is typically located under the rear driver’s side seat, integrated with the fuse block. You may need to lift the seat cushion to access it.
- âś” Disconnect and Remove: Carefully unplug all the electrical connectors from the BCM. They have locking tabs, so be gentle. Once disconnected, unbolt or unclip the module from its mounting location.
- âś” Install the New Module: Seat the cloned BCM into the mounting position and securely plug in all the electrical connectors. You should hear a ‘click’ as they lock into place.
- âś” Reconnect and Test: Reconnect the negative battery terminal. Turn the key to the ‘On’ position and test all functions: windows, locks, lights, radio, etc. Start the vehicle to ensure it runs correctly.
Important Post-Installation Notes
While our cloning service makes this a seamless process, some vehicles may require minor recalibrations. If your airbag light is illuminated, a professional scan tool is needed to perform the ‘Setup SDM Primary Key in BCM’ procedure. Additionally, a Brake Pedal Position Relearn might be necessary for proper brake light and traction control operation. These are simple procedures for any qualified technician.
Verified Vehicle Compatibility
This module is a direct-fit replacement for several GM SUVs. It is compatible with part numbers 15787809, 25802312, 8258023120, and 15135466. Please verify your part number or consult the list below. This part fits the following vehicles (without security system unless noted):
- 2005-2006 Envoy XL
- 2005-2009 Envoy
- 2005-2006 Trailblazer EXT
- 2005-2009 Trailblazer
- 2005-2007 Rainier
- 2005-2008 Isuzu Ascender
- 2006-2009 Saab 9-7X
Frequently Asked Questions
What is a Cloning Service?
Cloning is a service where we transfer the complete software and vehicle-specific data (like VIN and key information) from your original BCM to the replacement unit. This makes the new part plug-and-play, avoiding the need for expensive dealer programming.
Do I need to send my original BCM to you?
Yes. For the cloning service to work, we need your original module to extract the data. We will return your original module along with the newly programmed replacement. We do not keep your old part.
Will this fix my intermittent starting problem?
If your no-start issue is caused by the security system or other BCM-controlled functions, then yes, this is a very common fix. A faulty BCM is a primary cause of intermittent electrical and starting problems on these vehicles.
Is this a difficult part for a DIYer to install?
The physical replacement is straightforward for most DIYers with basic tools. It involves removing the rear seat cushion and unplugging connectors. Since we pre-program it, the most difficult part (software setup) is already done for you.
What if my airbag light comes on after installation?
This can happen occasionally. It simply means the BCM needs to be synced with the airbag module (SDM). A procedure called ‘Setup SDM Primary Key in BCM’ can be performed by any shop with a professional-grade diagnostic tool to resolve this.