Is Your Sierra Denali Running Rough?
If you’re experiencing frustrating issues like a persistent check engine light, poor fuel economy, erratic shifting, or even a no-start condition, the problem may lie with a failing Engine Control Module (ECM). As the central computer of your 2012-2016 Sierra Denali 2500, the ECM is responsible for managing everything from fuel injection and ignition timing to transmission shift points. When it begins to fail, the symptoms can be widespread and difficult to diagnose, but a replacement is often the definitive solution.
This genuine GM ECM, part number 12670335, is the direct-fit, reliable solution to restore your truck’s performance and dependability. The best part? We handle the complex programming for you. Simply provide your vehicle’s VIN during checkout, and our technicians will flash the module with the latest, most stable software updates directly from GM. This ensures perfect compatibility and function right out of the box, saving you a costly trip to the dealership and hours of diagnostic headaches.
From the Diagnostic Bay
We had a 2014 Silverado 2500 (which uses the same ECM) come into the shop with a complaint of harsh, unpredictable shifting and a P0700 transmission control system code. The owner had already replaced the transmission control module (TCM) and several solenoids with no improvement. After hours of chasing wires, we checked the data stream from the ECM and found it was intermittently dropping communication with the TCM. A new, properly programmed ECM like this one solved the “transmission” problem instantly. It’s a classic case of the brain, not the body, being the root cause.
Common Symptoms of a Failing ECM
- ✔ Persistent Check Engine Light (CEL) with various codes
- ✔ Engine stalling, stumbling, or misfiring
- ✔ Noticeable decrease in fuel efficiency
- ✔ Harsh or erratic automatic transmission shifting
- ✔ Complete no-start or intermittent starting issues
- ✔ Failure to communicate with diagnostic scan tools
- ✔ Warning lights on the dash such as “Service StabiliTrak”
Understanding Your 2012-2016 Sierra Denali 2500 ECM
The Engine Control Module is the nerve center of your truck’s powertrain. It processes information from dozens of sensors—like the crankshaft position sensor, oxygen sensors, and mass airflow sensor—to make thousands of calculations per second. These calculations dictate the precise amount of fuel to inject and when to create the spark for optimal power, efficiency, and emissions. A faulty module can disrupt this entire process, leading to the symptoms you’re experiencing. Our pre-programming service ensures that this replacement 2012-2016 Sierra Denali 2500 ECM has the correct software and calibrations for your specific vehicle configuration, including engine type, transmission, and emissions equipment.
Plug-and-Play Solution
We make the replacement process as simple as possible. By programming the unit to your VIN before shipping, we eliminate the need for expensive dealer-specific tools. Once you receive the module, the physical installation is straightforward. In most cases, you will only need to perform a simple security relearn procedure, which can be done without any special tools and typically takes about 30 minutes. This syncs the new ECM with your vehicle’s anti-theft system. Detailed instructions for this procedure are readily available and easy to follow.
This module is a direct replacement for multiple part numbers, including 12668866, 12668994, 12643636, 12663405, and more. It also fits a wide range of other GM vehicles, from the Chevy Cruze and Sonic to Express and Savana vans, ensuring a high-quality, widely-tested component.
Frequently Asked Questions
Do I need to get this ECM programmed?
No. We handle all the programming for you before we ship the part. Just provide us with your vehicle’s 17-digit VIN at checkout, and it will arrive ready for installation.
Where is the ECM located on my 2012-2016 Sierra Denali?
On the Sierra and Silverado trucks, the ECM is typically located in the engine bay, on the driver’s side, near the firewall or inner fender.
What is a VIN and why do you need it?
The VIN (Vehicle Identification Number) is a unique 17-digit code for your specific truck. We use it to load the exact GM-certified software and calibrations that your vehicle had when it left the factory, ensuring perfect compatibility with your engine, transmission, and other options.
Will this fix my check engine light?
If the check engine light is caused by a faulty ECM, then yes, this part will resolve the issue. It’s crucial to have a proper diagnosis to confirm the ECM is the point of failure, as other sensors or wiring issues can cause similar symptoms.
Is any other procedure needed after I install it?
Yes, you will likely need to perform a security relearn procedure (also known as a Passlock or anti-theft relearn). This process syncs the new ECM to your vehicle’s keys and can be done at home without special tools. The procedure typically involves turning the key to the ‘ON’ position for 10-15 minutes, three times in a row.
How do I give you my VIN?
You can add your VIN to the notes section during the checkout process. If you forget, don’t worry—we will contact you via email after your purchase to request it before we program and ship your module.