Is Your Cadillac STS Running Rough? The Solution is Here.
If you’re dealing with a frustrating check engine light, unpredictable stalling, poor fuel mileage, or a complete no-start condition in your 2009-2010 Cadillac STS, the root cause is often a failing Engine Control Module (ECM). As the central computer for your engine, when the ECM falters, it can create a cascade of baffling problems. I’ve seen it countless times in my 20+ years as a technician: owners replace sensor after sensor, only to find the core issue was the vehicle’s electronic brain all along.
A Technician’s Real-World Experience
“A customer’s 2009 STS with the 4.6L V8 came into my shop last month with these exact symptoms. It would start fine cold, but after 15 minutes of driving, it would stutter and die at stoplights. His scan tool showed a dozen random communication codes. We checked the wiring and grounds—all solid. The problem was internal failure within the original ECM. We installed one of these VIN-programmed modules, and the car ran perfectly, with all codes cleared. It’s a fix that saves time, money, and immense frustration.”
The Direct-Fit, Programmed Solution
This isn’t just a replacement part; it’s a complete solution. We take the guesswork and dealer hassle out of the equation. When you order, simply provide us with your vehicle’s VIN. Our experts will then flash this ECM with the latest, most stable GM-certified software specifically for your car. It arrives at your door ready for a straightforward installation.
- ✔ VIN Programmed: We load the correct software for your specific vehicle. No additional programming needed.
- ✔ Latest GM Updates: Your module comes with the newest software, addressing common factory bugs and improving performance and reliability.
- ✔ Solves Common Issues: A direct fix for error codes, harsh shifting, poor idling, and other ECM-related symptoms.
- ✔ Skip the Dealer: Avoid expensive dealership programming fees and long wait times. This is a true DIY-friendly solution.
Easy Installation Guide for Your 2009–2010 STS ECM
Replacing the ECM on your Cadillac STS is a manageable job for a home mechanic. On this model, you’ll typically find the module located on the left-hand (driver’s side) frame rail. Follow these steps for a successful installation:
- Safety First: Always disconnect the negative terminal from your car’s battery and wait at least 15 minutes for the system capacitors to discharge.
- Locate the ECM: Find the module mounted to the driver’s side frame rail in the engine bay area.
- Disconnect Connectors: Carefully unclip the wiring harness connectors from the old ECM. Inspect the pins on the harness side for any signs of corrosion or damage.
- Unbolt the Old Module: Remove the mounting bolts holding the old ECM in place and set it aside.
- Install the New ECM: Mount your new, pre-programmed ECM in the same location and secure it with the original bolts.
- Reconnect Everything: Firmly plug the wiring harness connectors into the new module. Reconnect your battery’s negative terminal.
- Final Check: Start the vehicle. The check engine light should be off, and the engine should run smoothly. A security relearn procedure may be required, which typically involves cycling the key.
Expert Pro Tip: Connector Health is Key
Before plugging in your new ECM, take a moment to spray the vehicle’s harness-side connectors with a quality electronics cleaner. Use a small, soft brush to gently clean away any dust or potential corrosion from the pins. A clean, solid connection is critical for the longevity and proper function of your new computer.
Guaranteed Compatibility
This Engine Control Module is a direct replacement for several GM service numbers. If your original module has any of the following numbers, this part is the correct fit for you:
Interchangeable Part Numbers: 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, 12678512
This Module Fits a Wide Range of GM Vehicles:
While this listing focuses on the Cadillac STS, this versatile ECM is also the correct part for the following vehicles. Please verify your specific engine and options.
- Cadillac CTS (2009): 6.2L
- Cadillac DTS (2009-2011)
- Cadillac SRX (2009): 4.6L
- Cadillac STS (2009-2010): 4.4L, 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)