Restore Your Sierra’s Performance and Reliability
Is your 2012-2016 GMC Sierra Denali 3500 running rough, throwing a persistent check engine light, or suffering from poor fuel economy? These are classic signs of a failing Engine Control Module (ECM), the central computer that manages your truck’s engine performance, fuel delivery, and emissions. A faulty ECM can cause a cascade of frustrating issues, leaving your powerful workhorse feeling sluggish and unreliable. This replacement ECM, part number 12663405, is the definitive solution to restore your truck’s factory performance and get you back on the road with confidence.
What sets this module apart is our professional programming service. Before we ship your part, we flash it with the latest official GM software updates, tailored specifically to your truck using its unique Vehicle Identification Number (VIN). This means no expensive trips to the dealership for programming. It arrives at your door ready for a straightforward installation, making this a perfect fix for both seasoned mechanics and skilled DIYers. By replacing your old unit with this correctly programmed 2012-2016 Sierra Denali 3500 ECM, you’re not just swapping a part—you’re ensuring your engine operates exactly as its designers intended.
Is Your Sierra Showing These Red Flags?
- ✔ Persistent Check Engine Light (CEL) that won’t clear.
- ✔ Diagnostic Trouble Codes (DTCs) related to internal module failure, such as P0601, P0606, or P060A.
- ✔ Communication error codes like U0100 (Lost Communication with ECM/PCM).
- ✔ Unexplained drop in fuel mileage.
- ✔ Engine cranks but refuses to start.
- ✔ Rough idling, stalling, or hesitation during acceleration.
- ✔ Harsh or erratic automatic transmission shifting.
A Technician’s Notebook
I remember a 2014 Sierra 3500 work truck that came into my bay with a bizarre set of symptoms. The owner complained of intermittent stalling at stoplights and a transmission that shifted hard into second gear, but only when the engine was warm. The scanner showed a P0606 (ECM Processor Fault) and a transmission code that didn’t make sense. After hours of chasing wiring diagrams, we suspected the ECM itself. The owner was hesitant due to the dealer’s high quote. We sourced a pre-programmed module like this one. The installation took less than 30 minutes, and upon startup, both the stalling and the harsh shifting were gone. The pre-flashed software corrected the internal logic flaw that was causing both issues. It saved the customer hundreds of dollars and a full day of shop labor.
A Straightforward Guide to Installation
- ✔ Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- ✔ Locate the ECM: On your Sierra, the ECM is typically located in the engine compartment on the driver’s side, near the firewall or inner fender.
- ✔ Disconnect Connectors: Carefully release the locking tabs on the large electrical connectors and pull them straight out from the module. Avoid damaging the pins.
- ✔ Remove Mounting Bolts: Unbolt the old ECM from its mounting bracket. There are usually three or four bolts holding it in place.
- ✔ Install the New Module: Seat the new, pre-programmed ECM onto the bracket and secure it with the mounting bolts.
- ✔ Reconnect and Secure: Plug the electrical connectors firmly back into the new module until they click into place. Reconnect the negative battery terminal.
- ✔ Perform Relearn (If Necessary): While this module is programmed, some vehicles require a security or crank-position relearn procedure. For many GM trucks, this can be done by cycling the key or may require a capable scan tool. Consult a service manual for your specific vehicle’s procedure.
Verified Vehicle Compatibility
This Engine Control Module is a direct-fit replacement for a wide range of GM vehicles. While this listing focuses on the 2012-2016 Sierra Denali 3500 ECM, it is also compatible with the following models and part numbers. Please verify your part number or contact us with your VIN to ensure perfect fitment.
Interchangeable Part Numbers: 12668866, 12668994, 12643636, 12663405, 12670335, 22819494, 12692200
- Buick Encore (2013-2016, 1.4L)
- Cadillac ELR (2014-2016)
- Chevrolet Cruze (2012-2016, 1.4L / Limited)
- Chevrolet Express 2500/3500 Van (2016, 4.8L/6.0L)
- Chevrolet Silverado 2500/3500 Pickup (2012-2016, 6.0L)
- Chevrolet Sonic (2012-2016, 1.4L)
- Chevrolet Spark (2014-2015, Gasoline)
- Chevrolet Suburban 3500 (2016)
- Chevrolet Trax (2013-2016)
- Chevrolet Volt (2011-2015)
- GMC Savana 2500/3500 Van (2016, 4.8L/6.0L)
- GMC Sierra 2500/3500 Pickup (2012-2016, 6.0L)
- GMC Sierra Denali 2500 (2012-2015, 6.0L)
- GMC Sierra Denali 3500 (2012-2016, 6.0L)
Do I really need to provide my VIN?
Do I really need to provide my VIN?
Yes, absolutely. Providing your VIN is critical. We use it to load the exact, correct GM software for your truck’s specific configuration, including engine, transmission, and emissions options. This ensures a true plug-and-play installation and prevents compatibility issues.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the original ECM (e.g., codes P0601, P0606), this replacement module will solve the problem. However, if the light is on due to a faulty sensor or other component, that separate issue will still need to be addressed.
Is any other programming required after installation?
In most cases, no additional programming is needed. The module is pre-flashed for your vehicle. Some GM models may require a simple key relearn or crankshaft position sensor relearn procedure, which can often be done without special tools. We recommend consulting a service manual for vehicle-specific steps.
How do I find my vehicle’s part number to confirm a match?
The part number is printed on a sticker on your original ECM. You can compare it to the list of compatible part numbers in our description. However, sending us your VIN is the most reliable way to guarantee a perfect match, as part numbers can supersede over time.