Is Your Sierra Denali 3500 Running Rough?
If you’re dealing with a persistent check engine light, erratic engine behavior, poor fuel mileage, or even a no-start situation in your 2012-2016 Sierra Denali 3500, a failing Engine Control Module (ECM) is a very likely culprit. As the central computer for your truck’s powertrain, when the ECM starts to fail, it can cause a cascade of frustrating and hard-to-diagnose issues. In my 20+ years in the shop, I’ve seen countless trucks where owners have replaced sensors and other parts, only to find the root cause was the ECM all along.
Expert Pro Tip: Check for External Failure Causes
Before you install your new ECM, take a minute to inspect the main wiring harness connectors for any corrosion, pushed-out pins, or moisture. On these workhorse trucks, the connectors can get contaminated. A poor connection can mimic ECM failure and, in worst-case scenarios, damage the new module. Cleaning the harness-side connectors with a dedicated contact cleaner is a 5-minute step that can save you hours of headaches.
The Direct, Programmed Solution
This isn’t just a replacement part; it’s a complete, ready-to-install solution. We take a genuine GM ECM and program it specifically to your truck’s Vehicle Identification Number (VIN). This critical step ensures all factory settings, security information, and operational parameters are a perfect match for your vehicle’s specific configuration.
- โ VIN-Programmed for Your Truck: We flash the module with the latest GM-certified software for your specific VIN.
- โ No Dealer Visit Required: Because it arrives pre-programmed, you can avoid the time and expense of a trip to the dealership for coding.
- โ Restores Peak Performance: A healthy ECM is key to proper fuel delivery, ignition timing, and transmission shifting, restoring the power and efficiency you expect.
- โ Clears Fault Codes: This module is the definitive fix for a wide range of diagnostic trouble codes (DTCs) related to processor, sensor, and communication failures.
Simple Installation for the DIYer or Professional
Replacing the ECM on your Sierra is a straightforward job that can be done with basic hand tools. It’s typically located in the front driver’s side of the engine compartment.
- Safety First: Always disconnect the negative battery terminal before beginning any electrical work.
- Locate and Disconnect: Find the ECM and carefully release the locking levers on the electrical connectors. Pull them straight out to avoid damaging the pins.
- Remove the Old Module: Unbolt the original ECM from its mounting bracket.
- Install the New Module: Secure your new, pre-programmed ECM onto the bracket and firmly reconnect the wiring harnesses until you hear and feel them click into place.
- Power Up: Reconnect the negative battery terminal. In most cases, the truck will start and run perfectly. Some vehicles may require a simple security relearn procedure, which can be found in your owner’s manual or online.
Guaranteed Fitment for Your 2012-2016 Sierra Denali 3500 ECM
This module, part number 12668991, is the correct replacement for your 2012-2016 Sierra Denali 3500 with the 6.0L engine. It also directly replaces a wide range of other GM part numbers, ensuring broad compatibility. If your original module has one of the following numbers, this is the correct part for you:
Interchangeable Part Numbers: 12668866, 12668994, 12643636, 12663405, 12670335, 22819494, 12692200.
While this is the primary computer for the Sierra 3500, it is also the correct module for many other GM vehicles, including the Silverado 2500/3500, Express/Savana Vans, Cruze, Sonic, and more. Please use the fitment chart to confirm compatibility with your exact model and options.
After purchase, simply reply to your order confirmation email with your vehicle’s 17-digit VIN, and we’ll handle the programming before it ships.