Is Your Sierra 3500 Running Rough? The ECM Might Be the Culprit.
The Engine Control Module (ECM), often called the engine computer, is the electronic brain of your 2012-2016 GMC Sierra 3500’s 6.0L engine. It meticulously manages everything from fuel injection and ignition timing to transmission shifts and emissions control. When this critical component begins to fail, it can cause a cascade of frustrating and seemingly unrelated problems, leaving your powerful workhorse feeling sluggish, unreliable, or even completely immobile. If you’re dealing with a persistent check engine light, poor fuel economy, or erratic engine behavior, you’ve come to the right place for a dependable solution.
From the Diagnostic Bay
We had a 2014 Silverado 2500 (which uses the same ECM) come into the shop with a bizarre complaint. The owner said it would randomly stall at stoplights, but only when the A/C was on. No consistent codes were stored, just a few random communication errors. We checked the battery, alternator, and all major grounds—everything looked perfect. After hours of chasing wires, we decided to inspect the ECM itself. We found subtle corrosion on one of the main connector pins, likely from moisture intrusion. Swapping in a pre-programmed ECM like this one not only solved the stalling issue but also improved the truck’s throttle response. It’s a reminder that the ECM’s health is fundamental to the entire vehicle’s operation.
Common Symptoms of a Failing ECM
- ✔ Persistent Check Engine Light (CEL) that won’t clear or returns immediately.
- ✔ Engine stalling, stumbling, or misfiring for no apparent reason.
- ✔ A noticeable drop in fuel efficiency.
- ✔ Difficulty starting the engine or a complete no-start condition.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Loss of power and poor acceleration.
- ✔ Communication errors with diagnostic scan tools.
The Plug-and-Play Solution: A Programmed 2012-2016 Sierra 3500 ECM
Don’t let a faulty engine computer keep your truck off the road. This genuine OEM replacement Engine Control Module, part number 12668991, is the definitive fix for your vehicle’s electronic woes. The biggest advantage of our service is that we program the module specifically for your truck before it ships. By providing us with your Vehicle Identification Number (VIN) during checkout, you receive a unit that is loaded with the latest GM factory software updates and is perfectly matched to your truck’s specific configuration. This eliminates the need for expensive dealership programming or specialized tools. It’s a true plug-and-play installation.
This module is a direct replacement for a wide range of original part numbers, ensuring compatibility and reliable performance. It is a direct fit for part numbers: 12668866, 12668994, 12643636, 12663405, 12670335, 22819494, and 12692200.
Wide-Ranging GM Compatibility
While this is the correct 2012-2016 Sierra 3500 ECM for the 6.0L engine, this versatile module was also used by General Motors in a variety of other vehicles, demonstrating its proven reliability. It is also a direct fit for models such as the Chevrolet Silverado 2500/3500, Express/Savana vans, Cruze, Sonic, Trax, Volt, Buick Encore, and more, as detailed in the fitment list. This cross-compatibility ensures you are getting a well-tested and widely-used component.
Frequently Asked Questions
Do I need to do any programming after I receive this ECM?
No. We flash the module with the latest GM software using your vehicle’s VIN before shipping. In most cases, it is a simple plug-and-play installation. However, some vehicles may require a security relearn procedure, which is a simple process that can be done without any special tools. Instructions are available upon request.
Where do I provide my VIN?
Please enter your 17-digit VIN in the notes section during checkout or send it to us via email after placing your order. We cannot program and ship the module without your vehicle’s VIN.
Is this a new or used part?
This is a high-quality, tested, and guaranteed good used OEM part. Each module is inspected and then programmed with fresh, vehicle-specific software to ensure optimal performance.
How do I install the ECM?
First, disconnect your vehicle’s battery. The ECM is typically located in the engine bay on the driver’s side. Carefully unplug the electrical connectors and unbolt the module. Install the new module, reconnect the connectors, and then reconnect the battery.
What if this doesn’t fix my problem?
We guarantee our programming and the functionality of the module. However, it is crucial to properly diagnose your vehicle’s issue before ordering. If the part is defective, we offer a replacement. Please contact us for warranty details and support.