Restore Your Vehicle’s Core Performance and Reliability
Is your Cadillac CTS, Corvette, or other GM vehicle acting erratically? Dealing with a persistent check engine light, sudden stalling, no-start conditions, or poor engine performance can be incredibly frustrating. As a technician with over two decades of experience, I’ve seen firsthand how a failing Engine Control Module (ECM) can disrupt your entire driving experience. The ECM is the brain of your engine, and when it falters, nothing works right. This isn’t just an inconvenience; it can be a serious safety concern.
This listing offers a direct, reliable solution: a replacement Engine Control Module, part number 12639300. We take the guesswork and high dealership costs out of the equation. Before we ship this module to you, our experts will program it with the latest official GM software updates, specifically matched to your vehicle’s unique Vehicle Identification Number (VIN). This ensures seamless communication with your car’s other systems, restoring the precise control and performance you expect.
From the Diagnostic Bay
I remember a 2009 CTS-V that came into the shop with a complaint that stumped two other mechanics. The owner described intermittent power loss and a transmission that seemed to have a mind of its own, but it never stored a consistent trouble code. After checking all the usual suspects—fuel pressure, sensors, wiring—I focused on the ECM. On the surface, it seemed fine. But by monitoring live data during a long test drive, I saw the processor voltage drop erratically under high engine temperatures. The heat soak was causing the ECM’s internal processor to fail. We installed a VIN-programmed module just like this one, and the car ran perfectly. It’s often these subtle electronic failures that cause the biggest headaches.
Is Your Vehicle Showing These Symptoms?
- ✔ Check Engine Light is illuminated with codes like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (ECM/PCM Processor Fault).
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained stalling, especially when the engine is warm.
- ✔ Noticeable decrease in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Communication errors with diagnostic scan tools.
A Straightforward Guide to Installation
Replacing your 2009 CTS Engine Control Module is a manageable job for a confident DIYer. Follow these general steps for a successful installation. Note: Location varies by model (e.g., RH front engine compartment on a CTS, lower air cleaner box on a Lucerne).
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts.
- Locate the ECM: Find the existing Engine Control Module on your vehicle. Consult a repair manual for your specific model if you’re unsure of the location.
- Disconnect Connectors: Carefully unlatch and remove the electrical wiring harnesses connected to the old ECM. Inspect the connectors for any corrosion or damage.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket and remove it from the vehicle.
- Install the New Module: Mount your new, pre-programmed ECM in place and secure the bolts.
- Reconnect Everything: Firmly plug the wiring harnesses back into the new ECM. Reconnect the negative battery terminal.
- Perform Security Relearn: In most cases, you will need to perform a security or anti-theft relearn procedure. 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 security system.
Verified Vehicle Compatibility
This module is a direct replacement for service number 12639300 and is interchangeable with 12636659, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512. It is confirmed to fit the following vehicles:
- Cadillac CTS 2009 (6.2L)
- Cadillac DTS 2009-2011
- Cadillac SRX 2009 (4.6L)
- Cadillac STS 2009 (4.4L, 4.6L), 2010 (4.6L)
- Cadillac XLR 2009 (ID 12636659 or 12625453)
- 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 (3.7L)
- Buick Lucerne 2009-2011 (4.6L)
- Saab 9-7X 2009
Frequently Asked Questions
Do I need to do any programming myself?
No. We handle all the programming before shipment. Simply provide your vehicle’s VIN during checkout, and we will flash the module with the correct, updated GM software for your specific vehicle.
What is a security relearn procedure?
This is a simple procedure that syncs the new ECM to your vehicle’s anti-theft system. It’s required for the vehicle to start and run. It usually involves a sequence of key turns and waiting periods and does not require special tools.
Is this a plug-and-play part?
Because it comes pre-programmed to your VIN, it is as close to plug-and-play as possible. After physical installation, the only remaining step is the security relearn, which you can do yourself in your driveway.
How do I find my part number to confirm a match?
The service number is printed on a sticker on your original ECM. This module replaces several part numbers, including 12639300, 12636659, and others listed in the description. Matching your vehicle model and engine in our fitment list is the most important step.
What happens if I don’t provide my VIN?
We cannot ship the module without your VIN. The programming is essential for the part to function in your vehicle. We will contact you after your purchase to get the VIN if it was not provided at checkout.