Restore Peak Performance to Your GM Truck
Is your 2012-2016 Sierra 2500, Silverado, or Express van suddenly running rough, refusing to start, or flashing a persistent check engine light? The Engine Control Module (ECM) is the brain of your vehicle’s powertrain, and when it starts to fail, it can cause a host of frustrating and complex issues. As a technician with over two decades of experience, I’ve seen firsthand how a faulty ECM can sideline even the toughest trucks. This isn’t just a part; it’s the central command for your engine’s performance, fuel economy, and reliability.
We take the guesswork and hassle out of the repair. This replacement Sierra 2500 Engine Control Module arrives at your door fully programmed with the latest GM software, tailored specifically to your vehicle’s VIN. This means no expensive trips to the dealership for programming and no need for specialized scan tools. It’s a direct-fit, ready-to-install solution designed to get your truck back to work.
A Technician’s Notebook: The Ghost in the Machine
I had a 2014 Sierra 2500 with the 6.0L in my bay that was a real head-scratcher. The owner complained of an intermittent no-start and occasional stalling at stoplights. There were no consistent trouble codes, just a random U0100 (Lost Communication with ECM) that would pop up and disappear. We checked grounds, wiring harnesses, and power feeds for hours. Everything seemed fine. On a hunch, I suggested we try a known-good ECM. We installed a pre-programmed unit, and the problems vanished instantly. The original ECM had an internal hairline fracture on the circuit board that would separate when it got hot, cutting communication. It’s a classic failure mode that can send you chasing ghosts for days if you don’t recognize the signs.
Is Your Sierra HD Acting Up?
A failing ECM can manifest in many ways. If you’re experiencing any of the following, your engine’s computer could be the culprit:
- ✔ Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error), P0606 (ECM/PCM Processor Fault), or U0100 (Lost Communication).
- ✔ Engine cranks but refuses to start.
- ✔ Unexplained drop in fuel mileage.
- ✔ Rough or unstable idle.
- ✔ Engine stalling or hesitating during acceleration.
- ✔ Transmission shifting issues or harsh engagement.
- ✔ Failure to pass an emissions test.
Straightforward Installation Guide for Your Sierra
Replacing your Sierra 2500 Engine Control Module is a manageable job for a DIYer with basic tools. Follow these steps carefully for a smooth installation.
- Safety First: Always disconnect the negative terminal from your truck’s battery and wait at least 15 minutes for the system to fully discharge.
- Locate the ECM: On most 2012-2016 Sierra/Silverado HD trucks, the ECM is located in the engine bay on the driver’s side, near the firewall or inner fender.
- Disconnect the Connectors: Carefully release the locking tabs on the electrical wiring harnesses and pull them straight out from the module. Never force them. Inspect the pins for any corrosion or damage.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket. There are typically a few 10mm bolts holding it in place.
- Install the New Module: Mount your new, pre-programmed ECM onto the bracket and secure it with the bolts.
- Reconnect Everything: Firmly plug the wiring harnesses back into the new ECM until they click into place. Reconnect the negative battery terminal.
- Final Step: In some cases, a security relearn procedure may be necessary. This can typically be done by turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times before starting the engine.
Verified to Fit These GM Models
This module is a direct replacement for part number 12668866 and is interchangeable with several other GM part numbers, including 12668994, 12643636, 12663405, and more. While it’s the primary computer for the Sierra and Silverado HD trucks, its versatile design was used across a wide range of GM vehicles. Please verify your part number or contact us with your VIN to ensure compatibility.
- GMC Sierra 2500/3500 Pickup (2012-2016) – 6.0L Engine
- Chevrolet Silverado 2500/3500 Pickup (2012-2016) – 6.0L Engine
- GMC Savana / Chevy Express 2500/3500 Van (2016) – 4.8L & 6.0L Engines
- Chevrolet Cruze (2012-2016) – 1.4L & Gasoline Models
- Buick Encore (2013-2016) – 1.4L Engine
- Chevrolet Sonic (2012-2016) – 1.4L Engine
- Chevrolet Trax (2013-2016)
- Chevrolet Volt (2011-2015)
- …and other models listed in the fitment data.
Frequently Asked Questions
Frequently Asked Questions
What does ‘VIN Programmed’ mean?
It means we load the module with the specific software and calibrations for your exact vehicle using the Vehicle Identification Number (VIN) you provide. This ensures it communicates correctly with all other modules on your truck, just like one from the factory.
Do I need to do anything after I install it?
In most cases, no additional programming is required. You may need to perform a simple ‘security relearn’ or ‘CASE relearn’ procedure, which can often be done without special tools. Instructions can be easily found online or in a service manual.
How do I provide my VIN?
After you complete your purchase, simply send us a message with your 17-digit VIN. We cannot ship your order until we receive this information, as the programming is essential for the part to function.
Will this fix my truck’s problem for sure?
This part corrects issues directly caused by a failing ECM. While it resolves the most common symptoms, it’s crucial to ensure your vehicle has been properly diagnosed. Problems with wiring, sensors, or fuel delivery can sometimes mimic ECM failure.
What if my original part number is not 12668866?
This module is a replacement for several part numbers, including 12668994, 12643636, and 12663405. Please check the full list of compatible part numbers in our description or contact us to verify fitment.