Restore Peak Performance and Reliability to Your GM Vehicle
Is your vehicle plagued by a persistent Check Engine Light, experiencing frustrating no-start conditions, or suffering from poor fuel economy and erratic performance? These are classic signs of a failing Engine Control Module (ECM), the electronic brain of your vehicle. In my 20+ years of experience, I’ve seen how a faulty ECM can cause a cascade of issues that are often misdiagnosed, leading to costly and unnecessary repairs. This replacement Engine Control Module, part number 12678512, is the definitive solution to get your vehicle running smoothly and efficiently again.
What sets this module apart is our professional programming service. Before we ship it, we flash the module with the very latest GM-certified software, specifically matched to your vehicle using the VIN you provide. This means you receive a part that is ready for installation right out of the box, eliminating the need for an expensive trip to the dealership for programming. For the DIY mechanic, this is a game-changer. For the professional shop, it’s a massive time-saver that frees up your diagnostic tools and service bays. By installing this expertly prepared 2009 Envoy Engine Module, you are not just replacing a part; you are restoring your vehicle’s core operational logic and communication network.
A Technician’s Notebook
I remember a 2010 Chevy Colorado that came into the shop with a maddeningly intermittent no-start condition. The owner had already replaced the battery and starter to no avail. We scanned it and found no active codes, but the data stream showed erratic sensor readings just before it would fail to crank. After ruling out wiring issues, we suspected the ECM. The internal processor was failing under certain temperature conditions, but not consistently enough to set a hard fault code like a P0606. We installed a pre-programmed ECM, and the problem vanished instantly. The customer was thrilled to have a reliable truck again, and we saved hours of diagnostic time by using a part we knew was properly configured from the start.
Is Your Vehicle Showing These ECM Failure Signs?
- ✔ Check Engine Light is illuminated with communication-related codes (e.g., U0100, P0601, P0606).
- ✔ Engine cranks but will not start, or experiences hard starting.
- ✔ Unexplained drops in fuel efficiency.
- ✔ Engine stalling, sputtering, or misfiring for no apparent reason.
- ✔ Automatic transmission shifting erratically or harshly.
- ✔ Apparent failure of multiple unrelated sensors at once.
A Straightforward Guide to Installation
Replacing your 2009 Envoy Engine Module is a manageable job for a confident DIYer. Always consult a vehicle-specific repair manual, but here is a general guide to the process:
- Safety First: Disconnect the negative terminal from your vehicle’s battery and wait at least 15 minutes to allow all system capacitors to discharge.
- Locate the ECM: On most of these vehicles, the ECM is found in the engine bay, often on the firewall or inner fender. The fitment list below specifies the location for each model (e.g., ‘LH engine’ or ‘RH firewall’).
- Disconnect Connectors: Carefully release the locking tabs on the wiring harness connectors and pull them straight out from the module. Never force them. Inspect the pins for any corrosion or 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 your new, pre-programmed ECM securely onto the bracket.
- Reconnect Everything: Firmly plug the wiring harnesses back into the new module until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn: After installation, you will need to perform a security relearn procedure (often called a Passlock or Passkey relearn). This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times. This allows the new ECM to sync with your vehicle’s anti-theft system. Your vehicle will not start until this is completed.
Verified Vehicle Compatibility List
This module is a direct replacement for multiple service numbers, including 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512. It is guaranteed to fit the following models and configurations. Please provide your VIN at checkout to ensure we provide a perfectly matched 2009 Envoy Engine Module or compatible unit for your specific vehicle.
Buick: DTS (2009-2011), Lucerne 4.6L (2009-2011)
Cadillac: CTS 6.2L (2009), SRX 4.6L (2009), STS 4.4L/4.6L (2009-2010), XLR (2009)
Chevrolet: Colorado (2009), Colorado 2.9L/3.7L (2010-2012), Corvette ZR1 (2009), Trailblazer 6.0L (2009)
GMC: Canyon (2009), Canyon 2.9L/3.7L (2010-2012), Envoy 5.3L (2009)
Hummer: H3 (2009), H3 3.7L (2010)
Saab: 9-7X (2009)
Frequently Asked Questions
Do I need to do anything after installing this ECM?
Yes. While the main engine programming is done for you, you MUST perform a security relearn procedure after installation. This syncs the new ECM with your vehicle’s anti-theft system and is required for the engine to start. This procedure does not require any special tools.
How do I provide my VIN number?
Simply enter your 17-digit Vehicle Identification Number (VIN) in the designated field during the checkout process. We cannot program and ship your module without it.
Is this part a direct replacement for all the service numbers listed?
Yes. This ECM is the modern, updated replacement for all the service numbers mentioned in the description, including 12636659, 12628993, and others. It incorporates the latest software and hardware revisions from GM.
Will this fix my specific problem?
This module corrects issues directly caused by a faulty ECM. While it resolves the most common symptoms like no-starts, stalling, and false sensor codes, it’s crucial to ensure your vehicle’s problem has been properly diagnosed. This part will not fix underlying mechanical or wiring issues.
What if I have questions during installation?
We are committed to your success. Our team of experienced technicians is available to help guide you through the process and answer any questions you may have about the installation or relearn procedure.