Restore Peak Performance to Your Vehicle’s Engine
Is your Cadillac STS, Corvette, or Hummer H3 suffering from erratic behavior, poor fuel economy, or a persistent Check Engine Light? These are classic signs of a failing Engine Control Module (ECM), the central computer responsible for managing your vehicle’s most critical functions. A faulty ECM can lead to frustrating and unpredictable driving experiences, from stalling at intersections to a complete no-start condition. This replacement Engine Control Module, part number 12678512, is the definitive solution to restore your vehicle’s original performance, reliability, and efficiency.
The ECM is the brain of your vehicle’s powertrain. It constantly analyzes data from dozens of sensors—like the oxygen sensors, crankshaft position sensor, and throttle position sensor—to make instantaneous adjustments to fuel injection, ignition timing, and transmission shifting. When it fails, the entire system is compromised. Instead of risking a costly and time-consuming trip to the dealership, we offer a streamlined, plug-and-play solution. We program this module specifically for your vehicle using your VIN, ensuring it arrives with the latest GM factory software updates. This eliminates the need for additional programming tools or dealer intervention, getting you back on the road faster.
From the Diagnostic Bay
We had a 2009 Cadillac CTS come in with a complaint of random stalling and a check engine light that multiple shops couldn’t solve. They had already replaced the fuel pump and a couple of sensors. After hooking up our diagnostic scanner, we noticed erratic data streams from the ECM and communication dropouts. Before condemning the computer, we did our due diligence: we checked all power and ground connections to the module and inspected the wiring harness for any signs of damage. Everything was perfect. This confirmed our suspicion. We installed a VIN-programmed ECM, performed the security relearn, and the car ran like new. It’s a powerful reminder that while the ECM is a robust component, it can be the root cause of many mysterious issues, and a correctly programmed replacement is the only proper fix.
Common Symptoms of a Failing Engine Control Module
- ✔ Persistent and illuminated Check Engine Light (CEL)
- ✔ Engine stalling or shutting off unexpectedly while driving
- ✔ Difficulty starting the engine or a complete no-start condition
- ✔ Noticeable decrease in fuel economy
- ✔ Rough idling, misfires, or hesitation during acceleration
- ✔ Harsh or incorrect automatic transmission shifting
- ✔ Communication errors with diagnostic scan tools
The Direct-Fit Solution: Your 2009-2010 STS Engine Module
This isn’t just a replacement part; it’s a comprehensive solution. The biggest hurdle in replacing a modern ECM is the complex software programming required to make it communicate with your specific vehicle’s systems. Our process handles this for you. When you place your order, you provide us with your vehicle’s VIN. Our technicians then flash this module with the correct, up-to-date software direct from GM. This ensures that the module is perfectly matched to your engine, transmission, and factory options. This 2009-2010 STS Engine Module is built to meet or exceed original equipment specifications, providing a reliable and long-lasting repair.
Wide-Ranging GM Compatibility
While this is a perfect fit for the Cadillac STS, this versatile E38 ECM was used across a wide range of GM vehicles. This module is a direct replacement for multiple service numbers, ensuring broad compatibility. Please verify your part number or consult our fitment list to confirm it is correct for your application. This unit is interchangeable with the following GM service numbers: 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512.
Installation is straightforward for an experienced DIYer or any professional mechanic. Once installed, you may need to perform a simple security relearn procedure (often called a CASE relearn or anti-theft relearn), which pairs the new ECM to your vehicle’s ignition and security system. This procedure can often be completed without special tools and instructions are widely available online or in service manuals.
Frequently Asked Questions
Do I need to have this module programmed by a dealer?
No. We handle the programming for you before shipment. Simply provide your vehicle’s VIN during checkout, and the module will arrive ready for installation with the latest GM software for your specific vehicle.
What is a VIN and where can I find it?
The VIN (Vehicle Identification Number) is a unique 17-digit code for your car. You can typically find it on a small plate on the driver’s side of the dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
Is installation difficult?
The physical installation is typically simple, involving disconnecting the battery, unplugging a few electrical connectors, and removing a few bolts. However, a security relearn procedure is often required after installation to sync the new module with your vehicle’s anti-theft system. This can often be done without special tools.
Will this part fix my vehicle’s problem for sure?
This module will resolve your issue if the original ECM has been correctly diagnosed as the point of failure. It’s crucial to ensure a proper diagnosis has been performed, as other components like sensors or wiring can cause similar symptoms.
What do all the different part numbers listed mean?
GM often releases updated versions of the same part under new service numbers. The numbers listed (12636659, 12639300, etc.) are all hardware-interchangeable versions of this ECM. Our module is a compatible replacement for all of them.
Does this part come with a warranty?
Yes, this part is backed by our standard warranty, which covers any defects in the module itself. Please see our warranty page for full details and conditions.