Restore Peak Performance to Your Silverado HD
As a technician with over two decades of experience under the hood, I know there’s nothing more frustrating than a powerful truck that won’t run right. If your 2012-2016 Silverado 3500 is suffering from a persistent check engine light, erratic behavior, or a no-start condition, a failing Engine Control Module (ECM) is often the culprit. This isn’t just a part; it’s the brain of your engine, and when it falters, everything from fuel economy to shifting can be affected. This replacement ECM, part number 12643636, is the reliable, straightforward solution to get your workhorse back in top form.
The biggest hurdle with ECM replacement has always been the programming. Dealerships charge a premium for this service, and it requires specialized equipment. We eliminate that step completely. Before this module ships, my team and I will program it with the latest GM software updates, using the specific Vehicle Identification Number (VIN) from your truck. This ensures it’s a true plug-and-play component, ready for installation the moment it arrives at your door.
Case Study: A Tricky Diagnosis
I recently had a 2014 Silverado 2500 (which uses the same ECM) in the bay with a bizarre issue. The owner complained of intermittent stalling at stoplights and a transmission that seemed to shift harshly out of nowhere. No specific transmission codes were stored, only a generic network communication code (U0100) and a history code for a processor fault (P0606). We checked all the wiring and grounds—they were perfect. On a hunch, we swapped in a known-good, properly programmed ECM. The problems vanished instantly. The original ECM’s internal processor was failing under load, corrupting communication to the other modules. This is a classic example of how a failing 2012-2016 Silverado 3500 ECM can cause symptoms that seem unrelated.
Is Your Silverado HD Showing These Signs?
A failing ECM can manifest in numerous ways. If you’re experiencing any of the following, it’s a strong indicator that your engine’s computer needs attention:
- ✔ Check Engine Light is on with codes like P0601, P0602, P0606, or U0100
- ✔ Vehicle will not start or is very difficult to start
- ✔ Noticeable drop in fuel efficiency
- ✔ Rough idling, stalling, or hesitation during acceleration
- ✔ Engine misfires or runs poorly
- ✔ Automatic transmission shifts erratically or harshly
- ✔ Failure to pass state emissions testing
A Straightforward Guide to Installation
Installing your new ECM is a manageable job for a DIYer with basic tools. Following these steps will ensure a smooth process. For the 2012-2016 Silverado 3500 ECM, the module is typically located in the front, left-hand side of the engine compartment.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the ECM: On your Silverado or Sierra HD, you’ll find it mounted near the coolant reservoir on the driver’s side of the engine bay.
- Disconnect the Connectors: Carefully release the locking tabs on the wiring harness connectors and pull them straight out from the module. 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 bolts holding it in place.
- Install the New ECM: Mount your new, pre-programmed ECM onto the bracket and secure it with the bolts.
- Reconnect Everything: Plug the wiring harnesses back into the new module, ensuring they click securely into place. Reconnect the negative battery terminal.
- Final Step: In some cases, a security or CASE relearn procedure may be required with a capable scan tool. However, with our VIN programming, the truck should start and run immediately.
Verified Compatibility for GM Vehicles
This engine control module is a direct replacement for part number 12643636 and other interchangeable numbers like 12668866, 12668994, and 12670335. It is confirmed to fit a wide range of General Motors vehicles. Please verify your part number or contact us with your VIN to ensure perfect compatibility.
- Chevrolet Silverado 2500/3500 Pickup (2012-2016) w/ 6.0L Engine
- GMC Sierra 2500/3500 Pickup (2012-2016) w/ 6.0L Engine
- GMC Sierra Denali 2500/3500 (2012-2016) w/ 6.0L Engine
- Chevrolet Express / GMC Savana 2500/3500 Van (2016) w/ 4.8L or 6.0L
- Chevrolet Suburban 3500 (2016)
- Chevrolet Cruze (2012-2016)
- Chevrolet Sonic (2012-2016)
- Chevrolet Trax (2013-2016)
- Chevrolet Volt (2011-2015)
- Chevrolet Spark (2014-2015)
- Buick Encore (2013-2016)
- Cadillac ELR (2014-2016)
Frequently Asked Questions
Frequently Asked Questions
Do I need to do any programming after I receive this ECM?
No. This module comes fully programmed to your vehicle’s VIN with the latest GM software. It is ready for installation right out of the box. A security relearn may be needed in some instances, which can be performed with many common scan tools.
How do I provide my VIN?
After you complete your purchase, you will need to send us your 17-digit VIN. You can typically add it as a note during checkout or send us a message through the platform. We cannot ship the part until we receive the VIN.
Is this compatible with other part numbers?
Yes, this ECM is a direct replacement for several part numbers, including 12668866, 12668994, 12643636, 12663405, 12670335, 22819494, and 12692200. If your original module has one of these numbers, this part will work.
Where is the ECM located on my 2015 Silverado 3500?
On the 2012-2016 Silverado and Sierra HD trucks with the 6.0L gas engine, the ECM is located in the engine compartment on the driver’s side, typically mounted to a bracket near the air filter box and coolant reservoir.
Will this fix my truck’s hard shifting problem?
In many cases, yes. The ECM controls engine performance, which directly impacts how the transmission is told to shift. If the ECM is sending bad data, it can cause poor shift quality. This is a common symptom of a failing module.