If you’re dealing with frustrating and unpredictable issues like your 2009 GMC Envoy stalling, poor fuel economy, or a persistent check engine light, you’ve likely traced the problem to its source: a failing Engine Control Module (ECM). As the ‘brain’ of your vehicle, a faulty ECM can cause a cascade of problems that are difficult to diagnose. This isn’t just an inconvenience; it’s a critical component failure that affects your vehicle’s performance and reliability. I’ve seen it countless times in my 20+ years in the shop—a perfectly good engine held back by a failing computer.
This isn’t just a replacement part; it’s a complete solution. We take the guesswork and extra cost out of the equation by professionally programming this ECM to your vehicle’s specific Vehicle Identification Number (VIN) before it ships. This means it arrives at your door with the latest GM software updates, ready for installation. You get to skip the expensive towing and programming fees at the dealership, turning a complex repair into a manageable job for a DIY enthusiast or a quick, profitable one for a professional mechanic.
A Technician’s Notebook: The Envoy That Wouldn’t Cooperate
I remember a 2009 Envoy that came into my bay with a laundry list of complaints: intermittent no-start, erratic shifting, and a check engine light that would come and go. The owner had already replaced the battery and alternator. The scan tool showed a mix of communication codes (U-codes) and a dreaded P0601 ‘Internal Control Module Memory Check Sum Error’. This code is a definitive sign of internal ECM failure. Instead of a costly dealership visit, we ordered a VIN-programmed module. The installation took less than 30 minutes, and after a simple security relearn, the Envoy ran like new. The customer saved hundreds and drove away with a reliable vehicle—that’s the power of a proper, pre-programmed part.
Is Your Vehicle Showing These Signs of ECM Failure?
A failing engine computer can manifest in numerous ways. If you’re experiencing any of the following, a faulty ECM is a likely culprit:
- ✔ Check Engine Light is illuminated with codes like P0601, P0606, or U0100.
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained drops in fuel efficiency.
- ✔ The transmission shifts harshly or at the wrong times.
- ✔ Noticeable loss of engine power or hesitation during acceleration.
- ✔ Stalling for no apparent reason, either while driving or at idle.
- ✔ Communication issues with your diagnostic scan tool.
Your Straightforward Installation Guide
Replacing your 2009 Envoy Engine Module is a manageable task. While specific steps can vary slightly by model, here is a general guide to get you started.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts.
- Locate the ECM: On the 2009 Envoy, the ECM is typically found in the engine bay on the driver’s side (LH engine). Consult a service manual for your specific vehicle if unsure.
- Disconnect Connectors: Carefully unlatch and remove the electrical wiring harness connectors from the old module. Be gentle, as these plastic clips can become brittle over time.
- 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 your new, pre-programmed ECM onto the bracket and securely fasten it.
- Reconnect Everything: Plug the wiring harness connectors firmly into the new module. Reconnect the negative battery terminal.
- Perform Security Relearn: Your vehicle may require a security relearn procedure to recognize the new ECM. This can typically be done without special tools (e.g., turn the key to ‘ON’ for 10-15 minutes, then ‘OFF’, and repeat 2-3 times before starting).
Verified Compatibility for Your Vehicle
This Engine Control Module is a direct-fit replacement for a wide range of GM vehicles. Please verify your make, model, and engine below. This unit is interchangeable with service numbers: 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512.
TRAILBLAZER 09 Electronic Control Module; (LH engine), 6.0L
SAAB 9-7X 09 Electronic Control Module; (LH engine)
COLORADO 09-12 Electronic Control Module; (RH firewall), 2.9L, 3.7L
CANYON 09-12 Electronic Control Module; (RH firewall), 2.9L, 3.7L
HUMMER H3 09-10 Electronic Control Module; (RH firewall)
CORVETTE 09 Electronic Control Module; (RH engine compartment), ZR1
CTS 09 Electronic Control Module; (RH front engine compartment), 6.2L
SRX 09 Electronic Control Module; (LH engine compartment), 4.6L
STS 09 Electronic Control Module; (LH frame rail), 4.4L, 4.6L
STS 10 Electronic Control Module; (LH frame rail), 4.6L
XLR 09 Electronic Control Module; (RH front engine compartment), ID 12636659 or 12625453
DTS 09-11 Electronic Control Module
LUCERNE 09-11 Electronic Control Module; (lower part of air cleaner box), 4.6L
The Smart Choice for a Lasting Repair
Don’t let a faulty computer keep your vehicle off the road. By choosing this pre-programmed 2009 Envoy Engine Module, you’re not just buying a part—you’re getting a reliable, cost-effective solution that restores your vehicle’s factory performance and gets you back behind the wheel with confidence. Provide your VIN at checkout and let us handle the complex part of the repair for you.
Frequently Asked Questions
Why do you need my VIN?
Your Vehicle Identification Number (VIN) contains critical information about your vehicle’s specific options, engine, and transmission. We use the VIN to load the exact, correct GM factory software and the latest updates onto the module, ensuring it communicates perfectly with your vehicle right out of the box.
Is any additional programming required after installation?
No. This ECM comes fully programmed to your VIN. The only step you may need to perform is a simple ‘security relearn’ or ‘key relearn’ procedure, which syncs the new module with your vehicle’s anti-theft system. This procedure typically requires no special tools and instructions can be easily found online for your specific model.
Will this fix my specific problem?
This module will correct issues directly caused by a failing ECM, such as internal processor faults (e.g., code P0601), communication errors, and driver circuit failures. It is essential to properly diagnose your vehicle to confirm the ECM is the point of failure before ordering.
Is this a brand new part?
This is a high-quality, tested, and verified original equipment part that has been professionally prepared for resale. Each unit is inspected and programmed with the latest software to ensure it meets or exceeds original factory performance standards.
What if I have a different part number on my original module?
This module, part number 12628911, is a direct replacement for several other GM service numbers, including 12636659, 12639300, and more, as listed in the compatibility section. As long as your vehicle is on our fitment list, this module will function correctly once programmed to your VIN.