Restore Your Truck’s Performance with a Reliable, Programmed ECM
There’s nothing more frustrating than a powerful truck like your 2012-2016 Sierra Denali 3500 that won’t run right. Whether you’re dealing with a persistent check engine light, poor fuel mileage, or a no-start condition, a faulty Engine Control Module (ECM) is often the culprit. As the central computer for your engine, its health is critical. This direct-fit ECM, part number 12670335, is the definitive solution to get your workhorse back on the road, operating with the precision and reliability you depend on.
We take the guesswork and hassle out of the repair. Unlike sourcing a module from a salvage yard or even the dealership, this unit arrives at your door pre-programmed with the latest official GM software updates. All we need is your vehicle’s VIN at checkout. This ensures perfect compatibility and function, eliminating the need for expensive scan tools or a costly trip to the dealer for programming. It’s a professional-grade fix designed for both seasoned mechanics and capable DIY enthusiasts.
A Technician’s Notebook: The Intermittent Gremlin
I had a 2015 Sierra 3500 with the 6.0L in my bay that was driving the owner crazy. It had an intermittent no-start and would occasionally throw a U0100 (Lost Communication With ECM/PCM) code, but by the time it got to the shop, it would start and run fine. We checked grounds, wiring harnesses, and power feeds—all solid. After days of diagnostics, we found that the ECM’s internal processor was failing under specific temperature conditions. It wasn’t a wiring issue; it was the computer itself. Swapping in a quality, correctly programmed Sierra Denali 3500 ECM like this one solved the problem instantly. It’s a reminder that sometimes the most elusive electrical gremlins live inside the module itself.
Is Your Sierra Exhibiting These ECM Failure Signs?
- ✔ Persistent Check Engine Light (CEL) with codes like P0601, P0606, or other internal processor faults.
- ✔ Complete no-start or crank-no-start condition where the engine turns over but won’t fire.
- ✔ Noticeable drop in fuel economy and overall engine performance.
- ✔ Erratic or harsh automatic transmission shifting.
- ✔ Stalling, rough idling, or engine misfires.
- ✔ Communication errors with diagnostic scan tools.
Your Straightforward ECM Installation Guide
- ✔ Safety First: Disconnect the negative terminal from your truck’s battery and wait 10-15 minutes for the system capacitors to discharge.
- ✔ Locate the ECM: On the 2012-2016 Sierra/Silverado HD trucks, the ECM is typically located in the front of the engine compartment on the driver’s side, near the battery and air filter housing.
- ✔ Disconnect the Connectors: Carefully release the locking tabs and unplug the large electrical connectors from the old module. Avoid forcing them.
- ✔ Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the hardware as you will reuse it.
- ✔ Install the New Module: Mount your new, pre-programmed ECM onto the bracket and securely fasten it.
- ✔ Reconnect Everything: Plug the electrical connectors firmly into the new module until they click into place. Reconnect the negative battery terminal.
- ✔ Final Steps: Your vehicle may require a security relearn procedure, which can often be done without special tools (instructions are easily found online or in your owner’s manual). Start the engine and let it idle to confirm the repair.
Verified Fitment for Your GM Vehicle
This module is a direct replacement for part number 12670335 and other interchangeable part numbers. While it is the correct hardware for a wide range of GM vehicles, this listing is specifically for a unit programmed for your 2012-2016 Sierra Denali 3500 with the 6.0L engine. It also fits other models like the Silverado 2500/3500, Express/Savana vans, and various GM cars when programmed accordingly. Please ensure your VIN is provided for correct programming.
Frequently Asked Questions
Why do you need my VIN?
Your Vehicle Identification Number (VIN) allows us to program the Engine Control Module with the exact software calibration file from GM for your truck’s specific engine, transmission, and emissions equipment. This ensures seamless integration and optimal performance without any additional programming.
Is any other programming required after installation?
No, this ECM arrives fully programmed and ready for installation. In some cases, a simple “security relearn” or “theft deterrent relearn” procedure is needed, which typically involves a sequence of key cycles. This does not require a dealer or special tools.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the ECM (common codes include P0601-P0606), then this part will resolve the issue. It’s always best to have the codes read by a scanner to confirm the diagnosis before ordering.
Does this part work for other engines besides the 6.0L gas V8?
No, the programming provided with this purchase is specifically for the 6.0L V8 engine found in the 2012-2016 GM HD trucks. While the hardware may be similar across other vehicles listed, the software is not interchangeable.
What if I have other part numbers like 12668866 or 12643636?
This module, part number 12670335, is a superseding and compatible replacement for a wide range of earlier part numbers including 12668866, 12668994, 12643636, and others. We ensure the programming matches your vehicle’s requirements.