Restore Peak Performance and Reliability to Your Vehicle
Is your Cadillac, Chevy, or GMC plagued by frustrating issues like stalling, erratic shifting, a persistent Check Engine Light, or a no-start condition? These are classic signs of a failing Engine Control Module (ECM). As a technician with over two decades of experience, I’ve seen how a faulty ECM can turn a reliable vehicle into a source of constant headaches. This isn’t just an inconvenience; it’s a critical component failure that affects fuel economy, emissions, and overall driveability. This replacement Engine Control Module, part number 12678512, is the definitive solution to get your vehicle running smoothly and dependably again.
What sets this part apart is our complimentary programming service. Before we ship your order, our specialists will flash this 2009 CTS Engine Module with the latest official GM software updates, precisely matched to your vehicle’s unique Vehicle Identification Number (VIN). This eliminates the need for an expensive trip to the dealership for programming, saving you hundreds of dollars and significant downtime. It arrives at your door ready for a straightforward installation, making it a perfect choice for both professional mechanics and capable DIY enthusiasts.
From the Diagnostic Bay: The Ghost in the Machine
A 2009 Cadillac CTS 6.2L rolled into my shop with a complaint that stumped two other mechanics. The owner described intermittent, harsh 2-3 shifts and occasional stalling at red lights, but with no consistent trouble codes. We checked the transmission fluid, solenoids, and wiring—all perfect. On a hunch, I monitored the live data from the ECM. I noticed the torque converter clutch command was flickering erratically, something the transmission module wasn’t requesting. This pointed directly to an internal fault in the ECM. After installing a VIN-programmed 2009 CTS Engine Module like this one, the ghost was gone. The car drove like new, proving that complex transmission symptoms can often originate in the engine’s computer.
Is Your GM Vehicle Showing These Symptoms?
- ✔ Engine stalling or misfiring for no apparent reason
- ✔ Unexplained drop in fuel efficiency
- ✔ Harsh or erratic automatic transmission shifting
- ✔ Vehicle refuses to start, even with a good battery and starter
- ✔ Check Engine Light is on with codes like P0601, P0606, or U0100
- ✔ Communication errors with other vehicle modules
A Straightforward Guide to Installation
- ✔ Safety First: Disconnect the negative terminal from your vehicle’s battery and wait 10 minutes for the system to fully discharge.
- ✔ Locate the ECM: On a 2009 CTS, the ECM is typically found in the right-hand front of the engine compartment. Consult a service manual for your specific vehicle’s location.
- ✔ Disconnect Connectors: Carefully release the locking tabs and unplug the wiring harness connectors from the old module. Avoid pulling on the wires themselves.
- ✔ 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 and securely fasten it.
- ✔ Reconnect Everything: Plug the wiring harnesses back into the new module until they click firmly into place. Reconnect the negative battery terminal.
- ✔ Perform Relearn Procedure: For many GM vehicles, a security relearn (often called a key cycle procedure) is required. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’, and repeating two more times before starting the engine. This allows the new ECM to sync with your vehicle’s anti-theft system.
Verified Vehicle Compatibility List
This module, part number 12678512, is a direct replacement for a wide range of GM vehicles. It is interchangeable with service numbers 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, and 12630464. Please verify your specific model and engine below:
CADILLAC DTS 09-11
CADILLAC SRX 09 (4.6L)
CADILLAC STS 09 (4.4L, 4.6L)
CADILLAC STS 10 (4.6L)
CADILLAC XLR 09
CHEVROLET COLORADO 09-12 (2.9L, 3.7L)
CHEVROLET CORVETTE 09 (ZR1)
CHEVROLET TRAILBLAZER 09 (6.0L)
GMC CANYON 09-12 (2.9L, 3.7L)
GMC ENVOY 09 (5.3L)
HUMMER H3 09-10 (3.7L)
BUICK LUCERNE 09-11 (4.6L)
SAAB 9-7X 09
Frequently Asked Questions
Do I really need to provide my VIN?
Yes, absolutely. Providing your VIN is essential. We use it to load the correct, vehicle-specific GM software and calibrations onto the module before shipping. This ensures perfect compatibility and function, saving you from a costly and time-consuming trip to the dealership for programming.
Is this a simple plug-and-play installation?
Because we program it to your VIN, it’s about as close to plug-and-play as you can get. After physical installation, you will likely need to perform a simple security relearn procedure, which can typically be done in your driveway without any special tools. We include general instructions for this process.
Will this fix my specific problem?
This module is the solution for failures internal to the ECM itself. While symptoms like stalling or no-start are common indicators of a bad ECM, it’s always best to have a proper diagnosis performed. A faulty sensor or wiring issue can sometimes mimic ECM failure. This part corrects issues stemming from the computer itself, such as those indicated by code P0601 (Internal Control Module Memory Check Sum Error).
What if my original part number is not 12678512?
No problem. This ECM is a direct replacement for several other GM service numbers, including 12636659, 12628993, and 12625453, among others listed in the description. As long as your vehicle is on our compatibility list, this module will function correctly once programmed to your VIN.
Is any other programming required after installation?
In most cases, no further programming is needed. The main engine and transmission software is pre-loaded. The only remaining step is the security relearn procedure to sync the module with your vehicle’s keys and anti-theft system, which you can do yourself.