Restore Your Vehicle’s Brain and Get Back on the Road with Confidence
Is your truck or SUV suffering from frustrating issues like a persistent Check Engine Light, poor fuel mileage, stalling, or a no-start condition? The Engine Control Module (ECM) is the central computer of your vehicle, managing everything from fuel injection and spark timing to transmission shifting. When it fails, it can cause a cascade of problems that are often difficult to diagnose. This is a direct-replacement, VIN-programmed 2009 Envoy Engine Control Module, designed to restore your vehicle’s factory performance and reliability.
As a technician with over two decades of experience, I’ve seen firsthand how a faulty ECM can mimic a dozen other component failures. Drivers often spend hundreds on sensors and parts they don’t need, only to find the root cause was the computer all along. We eliminate the guesswork and the expensive trip to the dealership. Simply provide your vehicle’s VIN during checkout, and our experts will flash this module with the latest, most stable software from GM specifically for your vehicle. It arrives at your door ready for installation, no additional programming required.
A Technician’s Notebook: The Envoy That Wouldn’t Cooperate
I remember a 2009 GMC Envoy that came into the shop with a list of complaints: intermittent stalling at red lights, hard shifting, and a check engine light that would come and go. The owner had already replaced the throttle body and a few sensors with no luck. A scan showed a mix of communication codes (U-codes) and a generic processor fault (P0606). This combination is a classic red flag for an internal ECM failure. The internal processors were failing under heat and load, causing unpredictable behavior. We installed a VIN-programmed module just like this one, and it was like a new vehicle. All symptoms vanished instantly. This isn’t just a part; it’s the solution that gets the job done right the first time.
Common Signs of a Failing Engine Computer
- ✔ Persistent Check Engine Light (CEL)
- ✔ Engine stalling or misfiring unpredictably
- ✔ Vehicle won’t start, but the battery and starter are good
- ✔ Poor engine performance and reduced power
- ✔ A significant drop in fuel economy
- ✔ Harsh or erratic automatic transmission shifting
- ✔ Diagnostic Trouble Codes (DTCs) such as P0601, P0606, or U0100
A Straightforward Guide to Installation
- ✔ Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- ✔ Locate the ECM: On most of these vehicles, the ECM is located in the engine bay, often on the firewall, inner fender, or near the air filter box. Refer to your vehicle’s service manual for the exact location.
- ✔ Disconnect Connectors: Carefully unlatch and remove the main electrical wiring harnesses from the old module. These connectors have locking tabs that must be released to prevent damage.
- ✔ Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the hardware as you may need to reuse it.
- ✔ Install the New Module: Mount the new, pre-programmed ECM in place and secure it with the original bolts.
- ✔ Reconnect Everything: Firmly plug the wiring harnesses back into the new ECM until they click into place. Reconnect the negative battery terminal.
- ✔ Final Step: In some cases, a security or crank relearn procedure may be needed, which can often be done without special tools. Check your service information for any vehicle-specific final steps.
Verified Vehicle Compatibility
This ECM, part number 12639300, is a direct replacement for a wide range of GM vehicles. It is also interchangeable with service numbers: 12636659, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512. Please confirm your vehicle is on the list below:
- Buick DTS: 2009-2011
- Buick Lucerne: 2009-2011 (4.6L)
- Cadillac CTS: 2009 (6.2L)
- Cadillac SRX: 2009 (4.6L)
- Cadillac STS: 2009 (4.4L, 4.6L), 2010 (4.6L)
- Cadillac XLR: 2009
- Chevrolet Colorado: 2009-2012 (2.9L, 3.7L)
- Chevrolet Corvette: 2009 (ZR1)
- Chevrolet Trailblazer: 2009 (6.0L)
- GMC Canyon: 2009-2012 (2.9L, 3.7L)
- GMC Envoy: 2009 (5.3L)
- Hummer H3: 2009-2010
- Saab 9-7x: 2009
Frequently Asked Questions
Do I need to get this programmed by a dealer?
No. We handle the programming for you before we ship the part. Just provide your vehicle’s 17-digit VIN when you order, and it will arrive ready to install.
Is this a new or used part?
This is a high-quality, tested, and verified replacement part that meets or exceeds original equipment specifications. We ensure every module is ready for long-term service.
Where do I find my VIN?
Your Vehicle Identification Number (VIN) can be found on your vehicle’s registration, insurance card, or on a small plate on the driver’s side dashboard, visible through the windshield.
What if my original part number is not 12639300?
This module is interchangeable with several other service numbers, including 12636659, 12628993, and others listed in the description. As long as your vehicle model is listed in our compatibility chart, this module will work.
Will this fix my transmission shifting problems?
In many GM vehicles, the ECM also controls transmission functions. If your shifting issues are caused by a faulty computer, this part is the correct solution. It’s a common symptom of ECM failure.