Restore Your Cadillac’s Core Performance and Reliability
Is your 2009-2010 Cadillac STS running rough, stalling unexpectedly, or showing a persistent Check Engine Light? These are classic signs of a failing Engine Control Module (ECM), the computer that serves as your vehicle’s brain. A faulty ECM can cripple your engine’s performance, fuel efficiency, and overall drivability. As a technician with over two decades of experience, I’ve seen firsthand how a failing module can cause a cascade of frustrating, hard-to-diagnose issues. This isn’t just a part; it’s the solution to getting your vehicle back to its smooth, responsive self.
This isn’t just any replacement part. We provide a fully programmed Engine Control Module, part number 12678512, tailored specifically to your vehicle. Simply provide your Vehicle Identification Number (VIN) during checkout, and our experts will program the module with the latest GM factory software updates. This critical step ensures seamless communication with your car’s other systems, eliminating the need for an expensive trip to the dealership for programming. It arrives at your door ready for installation.
From the Diagnostic Bay: The Ghost in the Machine
I remember a 2010 Cadillac STS that came into my shop with a complaint of intermittent stalling and a random misfire that no one could pin down. The owner had already replaced spark plugs, coils, and even a fuel pump at another garage. The codes were all over the place—U0100 for lost communication, P0300 for random misfires, and P0606 for an internal processor fault. After verifying the wiring and grounds were solid, experience pointed me straight to the ECM. These modules, when they start to fail, can send erratic signals that mimic other component failures, costing owners hundreds in unnecessary repairs. We installed a VIN-programmed ECM, and the car ran perfectly. It’s a powerful reminder that starting with the ‘brain’ is often the most direct path to a fix.
Is Your Cadillac Exhibiting These ECM Failure Signs?
A failing computer can manifest in numerous ways. If you’re experiencing any of the following, a faulty 2009-2010 STS ECM is a likely culprit:
- ✔ Check Engine Light is illuminated with codes like P0601, P0602, P0606, or U-series communication codes.
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained drops in fuel economy.
- ✔ The vehicle stalls for no apparent reason, either while driving or at idle.
- ✔ Noticeable hesitation or stumbling during acceleration.
- ✔ Automatic transmission shifts harshly or at the wrong times.
- ✔ Other warning lights on the dashboard (e.g., ABS, Traction Control) illuminate due to communication loss.
A Straightforward Guide to Installation
Installing your new ECM is a manageable task for a confident DIYer. Following these steps will ensure a smooth process. Always consult a vehicle-specific repair manual for detailed instructions and torque specifications.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental reconnection.
- Locate the ECM: On the 2009-2010 Cadillac STS, the ECM is typically located on the driver’s side frame rail. It’s a silver metal box with several large electrical connectors.
- Disconnect Wiring: Carefully release the locking tabs on each electrical connector and pull them straight out from the module. Never force them. Inspect the connectors for any corrosion or damage.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the hardware safe as you will need it for the new module.
- Install the New ECM: Mount your new, pre-programmed 2009-2010 STS ECM onto the bracket and secure it with the original hardware.
- Reconnect Wiring: Plug the electrical connectors firmly back into the new module. You should hear or feel a click as they lock into place.
- Final Step: Reconnect the negative battery terminal. The vehicle may need to complete a security relearn procedure, which often involves turning the key to the ‘ON’ position for 10-15 minutes. Check your owner’s manual for specific instructions.
Verified Vehicle Compatibility
This module is a direct replacement for service number 12678512 and is interchangeable with part numbers 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, and 12630464. While this listing is focused on the Cadillac STS, it also fits a wide range of GM vehicles. Please verify your part number and application below:
- Cadillac STS (2009): 4.4L & 4.6L
- Cadillac STS (2010): 4.6L
- Cadillac CTS (2009): 6.2L
- Cadillac DTS (2009-2011)
- Cadillac SRX (2009): 4.6L
- Cadillac XLR (2009): ID 12636659 or 12625453
- Buick Lucerne (2009-2011): 4.6L
- 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 option
- Saab 9-7X (2009)
Frequently Asked Questions
What is VIN programming and why is it necessary?
VIN programming loads your vehicle’s specific identification number and related software into the ECM. This ensures it communicates correctly with the engine, transmission, anti-theft system, and other modules. We handle this for you so the part is ready to install, saving you a dealership visit.
Is this part truly plug-and-play?
Because we program the module to your VIN before shipping, it is designed to be as close to plug-and-play as possible. In some cases, your vehicle may require a simple security or crankshaft position sensor relearn procedure, which can typically be done without special tools.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the original ECM (e.g., codes P0601-P0606), then this replacement module will solve the problem. However, if the light is on due to another faulty sensor or component, that issue will still need to be addressed.
Do I need to send my old ECM (core) back?
No core charge or return is required for this purchase. You can recycle your old module locally.
How do I provide my VIN?
Simply enter your 17-digit VIN in the designated field during the checkout process. Please double-check it for accuracy to ensure correct programming.