Restore Full Electrical Function to Your Isuzu Ascender
If you’re dealing with baffling electrical problems in your Isuzu Ascender, GMC Envoy, or Chevy Trailblazer, a failing Body Control Module (BCM) is often the culprit. As a technician with over 20 years of experience, I’ve seen firsthand how a faulty BCM can turn a reliable SUV into a source of constant frustration. From power windows that won’t cooperate to a dashboard that lights up like a holiday tree for no reason, these issues point directly to the vehicle’s central nervous system for body electronics. This isn’t just an inconvenience; it can affect safety systems and your vehicle’s overall performance.
This replacement Body Control Module, part number 15135466, is the definitive solution. What sets our service apart is our professional cloning process. You send us your original BCM, and we transfer all its critical data—including immobilizer information, mileage, and specific vehicle options—to this replacement unit. The result? A module that is truly plug-and-play. No expensive trips to the dealership for programming, no complex diagnostic tools required for the initial setup. We handle the technical work so you can get back on the road with confidence.
A Technician’s Notebook
I remember a 2006 Trailblazer that came into the shop with a laundry list of bizarre, intermittent complaints. The radio would turn on and off by itself, the driver’s side power lock was dead, and the dome light would flicker while driving. The owner had already replaced the battery and checked all the fuses. After connecting my scan tool, I found multiple ‘Loss of Communication’ codes with the BCM. Instead of a costly diagnostic path, we pinpointed the BCM. By using a cloning service like this one, we had the customer’s vehicle fixed the next day with a simple swap, saving them hundreds compared to a new module and dealership programming fees.
Common Signs of a Failing BCM
A failing BCM can manifest in numerous ways. If your vehicle is experiencing any of the following, it’s a strong indicator that your BCM needs attention. Look out for communication-related Diagnostic Trouble Codes (DTCs), often in the U-series (e.g., U0140, U0155).
- ✔ Erratic or non-functional power windows, door locks, or mirrors.
- ✔ Interior or exterior lights that stay on, flicker, or don’t work at all.
- ✔ The security or anti-theft system preventing the engine from starting.
- ✔ Horn honking unexpectedly or not working when pressed.
- ✔ Inconsistent or failed operation of the windshield wipers.
- ✔ False warnings appearing on the instrument cluster.
- ✔ Inability of a diagnostic scan tool to communicate with the module.
A Straightforward Guide to Installation
Installing your cloned 2005-2008 Ascender BCM is a manageable job for a DIY enthusiast. The BCM is typically located as part of the front fuse box assembly. Following these steps will ensure a smooth replacement.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts.
- Locate the BCM: On these GM SUVs, the BCM is integrated with the fuse box under the rear seat on the driver’s side. You will need to remove the seat cushion to access it.
- Disconnect Connectors: Carefully unplug all the electrical connectors from the BCM/fuse box assembly. These connectors have locking tabs that must be depressed to be removed. Do not force them.
- Remove the Old Module: Unbolt the old BCM/fuse box assembly from its mounting points and remove it from the vehicle.
- Install the New Module: Mount your new, pre-programmed BCM in the same location and securely fasten it.
- Reconnect Everything: Plug all electrical connectors back into their correct ports. They are often color-coded or keyed to only fit in the correct spot. Reconnect the negative battery terminal.
- Perform Post-Install Checks: Start the vehicle and test all body functions—lights, locks, windows, wipers, etc. Note the post-installation procedures below, as some relearns may be necessary.
Important Post-Installation Steps
While our cloning service makes this a near plug-and-play repair, some vehicle systems may require recalibration after the new module is installed. Please be aware of the following potential procedures:
- Airbag System Sync: If the airbag warning light is illuminated after installation, a professional scan tool is needed to perform the ‘Setup SDM Primary Key in BCM’ procedure. This syncs the BCM with the airbag module.
- Brake Pedal Position Relearn: On some models, a brake pedal position sensor relearn may be required to ensure the brake lights and traction control system function correctly.
Disclaimer: Specific requirements can vary. Always consult a factory service manual or a qualified technician for guidance.
Will This Fit My SUV?
This BCM is a direct-fit replacement for several GM models. Please verify your vehicle and options below. This module replaces part numbers 15135466, 25802312, 8258023120, and 15787809.
- Buick Rainier: 2005-2007 (front, fuse box side, w/o security system)
- Chevrolet Trailblazer: 2005-2009 (front, fuse box side, w/o security system)
- Chevrolet Trailblazer EXT: 2005-2006 (front, fuse box side, w/o security system)
- GMC Envoy: 2005-2009 (front, fuse box side, w/o security system)
- GMC Envoy XL: 2005-2006 (front, fuse box side, w/o security system)
- Isuzu Ascender: 2005-2008 (front, fuse box side, some w/o security system)
- Saab 9-7X: 2006-2009 (fuse box front)
Frequently Asked Questions About the 2005-2008 Ascender BCM
What is a Cloning Service?
Cloning is a process where we transfer the essential data from your original, failing BCM directly onto the replacement unit. This includes the VIN, mileage, and vehicle-specific option configurations. This makes the replacement module plug-and-play, avoiding the need for expensive dealership programming.
Why do you need my original BCM?
We need your original module to extract the unique data that makes your vehicle operate correctly. Without this data, the replacement BCM would not be able to communicate with other modules in your vehicle, leading to a no-start condition or other system failures.
Do I get my old module back?
Absolutely. Your original module is always returned to you along with the programmed replacement unit. We do not keep the core part.
What if my airbag light comes on after installation?
This is a known possibility. It means the new BCM needs to be electronically ‘introduced’ to the airbag system’s Sensing and Diagnostic Module (SDM). A professional scan tool is required to perform the ‘Setup SDM Primary Key in BCM’ procedure to clear the light.
Is this a difficult part to replace myself?
For someone with basic mechanical skills, it’s very manageable. The BCM is part of the rear fuse block, which is located under the rear seat. The main challenge is carefully disconnecting and reconnecting the various wiring harnesses. No special tools are typically needed for the removal and installation itself.