Programmed 2012-2016 Sierra Denali 2500 ECM 12670335 Engine Control Module

Is Your Sierra Denali Running Rough? Get a Reliable, Programmed Solution.

If you’re dealing with a frustrating no-start condition, erratic idling, poor fuel economy, or a persistent Check Engine Light on your 2012-2016 Sierra Denali 2500, a failing Engine Control Module (ECM) is a very likely culprit. As the brain of your truck’s engine, when the ECM starts to fail, it can cause a cascade of confusing and costly problems. You don’t have to keep throwing parts at the problem or face an expensive bill and long wait at the dealership.

This is a direct-fit replacement ECM, part number 12670335, that arrives at your door fully programmed to your truck’s specific Vehicle Identification Number (VIN). We handle the complex part for you. By flashing the module with the latest official GM software updates before it ships, we ensure it communicates perfectly with your truck’s existing systems right out of the box.

The “Plug & Play” Difference: My Experience

A customer’s 2014 Sierra 2500 with the 6.0L came into my shop last month with exactly these symptoms. The owner had already replaced spark plugs, coils, and even the throttle body trying to chase down a persistent P0300 random misfire code and harsh, unpredictable shifting. After confirming power and grounds to the module were solid, my diagnostic scanner pointed to an internal ECM fault. Instead of a costly dealer replacement, we used one of these VIN-programmed modules. The swap took less than 30 minutes, and the truck ran perfectly on the first key turn. No additional programming, no dealer visits—just a straightforward fix. That’s the value we provide.

Common Symptoms of a Failing Sierra Denali 2500 ECM

If you’re experiencing any of the following, your ECM is the most probable cause:

• ✔ Engine cranks but refuses to start.
• ✔ Unexplained Check Engine Light (CEL) with various communication or sensor codes.
• ✔ Noticeable drop in fuel mileage.
• ✔ Rough or unstable idle.
• ✔ Engine stalling or hesitating, especially under load.
• ✔ Harsh or incorrect automatic transmission shifting.
• ✔ Communication errors with diagnostic scan tools.

Simple Installation: Get Your Truck Back on the Road

Installing your new ECM is a straightforward process that you can do in your own driveway. No specialized tools are required.

1. Safety First: Disconnect the negative terminal from your truck’s battery.
2. Locate the ECM: On your Sierra, the ECM is typically located in the front left (driver’s side) of the engine compartment, often near the battery or air filter housing.
3. Disconnect Connectors: Carefully release the locking tabs on the wiring harness connectors and pull them straight out from the module.
4. Remove the Old Module: Unbolt the old ECM from its mounting bracket and remove it from the vehicle.
5. Install the New Module: Bolt your new, pre-programmed ECM into place.
6. Reconnect Everything: Firmly plug the wiring harnesses back into the new ECM until they click, ensuring a secure connection. Reconnect your battery terminal.
7. Final Step: Your truck is now ready to start. In some cases, a security relearn procedure may be necessary, which can typically be done by cycling the key and is detailed in your owner’s manual.

Guaranteed Compatibility

This module is a direct replacement for a wide range of GM vehicles and supersedes multiple part numbers. Simply provide your VIN at checkout, and we’ll ensure it’s a perfect match. This unit is compatible with the following part numbers:

12668866, 12668994, 12643636, 12663405, 12670335, 22819494, 12692200

While this listing is for the Sierra Denali 2500, this versatile ECM also fits many other GM models, including the Silverado 2500/3500, Express/Savana Vans, Cruze, Sonic, Trax, and more. Order with confidence knowing you’re getting the right part, programmed correctly, the first time.