Restore Peak Performance and Reliability to Your GM Truck or Van
Is your truck suffering from baffling issues like intermittent stalling, a persistent check engine light, or a complete no-start condition? As a technician with over two decades of experience, I’ve seen firsthand how a failing Engine Control Module (ECM) can wreak havoc, sending both owners and mechanics down a frustrating diagnostic rabbit hole. The ECM is the brain of your engine, and when it falters, everything from fuel delivery to spark timing and transmission shifting can become erratic. This isn’t just an inconvenience; it’s a critical failure that compromises your vehicle’s performance and safety.
This genuine GM Engine Control Module, part number 12668991, is the definitive solution. What sets our service apart is that we take the biggest headache out of the repair: programming. Before this module ever leaves our facility, we flash it with the latest official GM software, precisely matched to your truck using the Vehicle Identification Number (VIN) you provide. This means you receive a part that is truly ready for installation, saving you a costly trip to the dealership and hours of potential downtime.
Case Study: A Tricky Diagnosis
I remember a 2014 Silverado 2500 with the 6.0L V8 that came into the shop on a flatbed. The owner had replaced the battery, alternator, and even the fuel pump, but it still wouldn’t start consistently. It had no spark and the fuel injectors weren’t firing, but there were no clear trouble codes—just a generic ‘U0100 Lost Communication’ code that would pop up intermittently. After hours of checking wiring harnesses and grounds, we tested the ECM itself. We found that the main processor was failing under load. We installed a VIN-programmed module just like this one, and the truck fired up on the first try and ran perfectly. It’s a classic example of how a faulty ECM can mimic other failures, making a direct replacement the only real fix.
Is Your Truck’s Brain on the Fritz?
A failing ECM can manifest in numerous ways. If you’re experiencing any of the following, your engine’s computer is the likely culprit:
- âś” Check Engine Light is illuminated with codes like P0601 (Internal Control Module Memory Check Sum Error), P0606 (ECM/PCM Processor Fault), or U0100 (Lost Communication with ECM).
- âś” Engine cranks but refuses to start.
- âś” Unexplained stalling, especially when coming to a stop or at idle.
- âś” Noticeable drop in fuel economy.
- âś” Poor engine performance, hesitation, or misfiring.
- âś” Harsh or erratic automatic transmission shifting.
Your Straightforward ECM Installation Guide
Replacing the ECM on your Sierra or related GM vehicle is a manageable job for a confident DIYer. Our pre-programming service makes it even simpler. Follow these general steps to get back on the road:
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent any accidental reconnection.
- Locate the ECM: On most 2012-2016 Sierra and Silverado trucks with the 6.0L engine, the ECM is located in the front left (driver’s side) of the engine compartment, often mounted to the fender or a bracket near the airbox.
- Disconnect the Connectors: Carefully release the locking tabs on the large electrical harness connectors and pull them straight out from the module. Avoid pulling on the wires themselves. There may be two or three main connectors.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the hardware, as you will need it to install the new unit.
- Install the New Module: Bolt your new, pre-programmed ECM into place. Reconnect the electrical harnesses, ensuring they click securely into position and the locking tabs are engaged.
- Reconnect the Battery: Reattach the negative battery terminal. In some cases, you may need to perform a simple security relearn procedure, which typically involves turning the key to the ‘ON’ position for 10-15 minutes. Consult your vehicle’s service information for specific steps if required.
Verified Fitment Across the GM Family
While this is a primary replacement for the 2012-2016 Sierra 3500 ECM, this module’s versatile architecture allows it to be programmed for a wide range of GM vehicles. It is a direct replacement for multiple part numbers, including 12668866, 12668994, and 12643636. Key compatible models include:
- âś” 2012-2016 Chevrolet Silverado & GMC Sierra 2500/3500 Pickups (6.0L Gas Engine)
- âś” 2016 Chevrolet Express & GMC Savana 2500/3500 Vans (4.8L & 6.0L Gas Engines)
- âś” 2011-2015 Chevrolet Volt
- âś” 2012-2016 Chevrolet Sonic (1.4L & other gas engines)
- âś” 2012-2016 Chevrolet Cruze (Gas engines)
- âś” 2013-2016 Buick Encore (1.4L) & Chevrolet Trax
To ensure perfect compatibility, we program the module based on the VIN you provide at checkout. This guarantees it functions exactly as the original did from the factory.
Do I need to take this ECM to a dealer for programming?
Do I need to take this ECM to a dealer for programming?
No. The main benefit of our service is that we handle all the programming for you before we ship the part. Simply provide your vehicle’s 17-digit VIN during or after checkout, and we will flash the module with the correct, updated GM software for your specific vehicle.
Is this installation difficult for a DIY mechanic?
The physical replacement is straightforward, involving basic hand tools to unbolt the old module and install the new one. Because we pre-program it, you avoid the most complex part of the job. Some vehicles may require a simple ‘security relearn’ procedure, which can be done without special tools.
What information do you need from me?
We need your vehicle’s 17-digit Vehicle Identification Number (VIN). You can typically find this on your dashboard (visible through the driver’s side of the windshield) or on the driver’s side door jamb sticker. Please provide it after purchase so we can ensure perfect programming.
Will this fix my specific problem, like poor fuel mileage?
If your issues, such as poor fuel economy, erratic shifting, or a no-start condition, are caused by a faulty ECM, then this part is the correct solution. It restores the factory-specified control over all engine and transmission parameters.
Does this module fit other part numbers?
Yes, this module is a direct, programmable replacement for a variety of GM part numbers, including 12668866, 12668994, 12643636, 12663405, 12670335, 22819494, and 12692200, among others. Our VIN-matching process ensures it works for your application.