Restore Your Truck’s Brain, Not Just a Part
As a technician with over two decades of experience under the hood, I’ve seen firsthand the frustration a failing Engine Control Module (ECM) can cause. Your 2012-2016 Sierra Denali 2500 isn’t just a truck; it’s a workhorse, and when it’s down, everything stops. You might be dealing with a persistent Check Engine Light, rough idling, stalling, or a complete no-start condition. These aren’t just annoyances—they’re signs that the central computer of your engine is in distress. This isn’t the time for guesswork; it’s time for a reliable, professional-grade solution.
This isn’t just a replacement part; it’s a complete fix. We are providing a genuine GM Engine Control Module, part number 12670335, that comes fully programmed to your truck’s specific Vehicle Identification Number (VIN). Before we ship it, we flash it with the latest, most stable software updates directly from GM. This critical step ensures seamless communication with your vehicle’s other modules, restoring factory performance, fuel efficiency, and drivability. You get to skip the expensive trip to the dealership for programming—a process that can often cost hundreds of dollars on its own.
Case Study: A Tricky Diagnosis
I remember a 2014 Sierra 2500 that came into my bay with an intermittent no-start condition that was driving the owner crazy. It would be fine for weeks, then suddenly refuse to crank. There were no consistent trouble codes, just a random U0100 (Lost Communication with ECM) that would pop up and disappear. We checked grounds, wiring harnesses, and power feeds for days. Finally, on a hunch, we monitored the ECM’s internal temperature data and noticed it would go offline right as it got heat-soaked. A replacement, pre-programmed 2012-2016 Sierra Denali ECM solved the problem permanently. It’s often these subtle internal failures, not just hard codes, that require a quality replacement.
Is Your Truck Showing These Symptoms?
A failing ECM can manifest in numerous ways. If you’re experiencing any of the following, this module is the likely solution. Cross-reference these symptoms with diagnostic trouble codes (DTCs) for a confident diagnosis.
- ✔ Check Engine Light is illuminated with codes like P0601, P0602, P0606 (ECM/PCM Processor Fault) or U0100.
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained drops in fuel economy.
- ✔ Rough or erratic engine idling and stalling.
- ✔ Noticeable loss of power and poor acceleration.
- ✔ Harsh or incorrect automatic transmission shifting.
- ✔ Communication issues with your scan tool.
A Straightforward Guide to Installation
Replacing your 2012-2016 Sierra Denali ECM is a manageable job for a DIY enthusiast. Since this unit arrives pre-programmed, no special computer tools are needed for the installation itself. However, please note that some vehicles may require a security relearn procedure, which can typically be done without special tools. Instructions are readily available online for your specific model.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental reconnection.
- Locate the ECM: On most Sierra/Silverado HD trucks, the ECM is located in the front of the engine bay, on the driver’s side, near the air filter housing.
- Disconnect Connectors: Carefully release the locking tabs and unplug the wiring harness connectors from the old module. Inspect them for any corrosion or damage.
- 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 wiring harness connectors firmly into the new module until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn: If your truck does not start, perform the security relearn procedure. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times.
Verified Vehicle Compatibility
This ECM is a direct replacement for multiple part numbers, including 12668866, 12668994, 12643636, 12663405, 22819494, and 12692200. It is guaranteed to fit the following GM vehicles, provided the options match. Please provide your VIN upon purchase to ensure perfect programming.
Chevrolet: Cruze (2012-2016), Express 2500/3500 Van (2016), Silverado 2500/3500 Pickup (2012-2016), Sonic (2012-2016), Spark (2014-2015), Suburban 3500 (2016), Trax (2013-2016), Volt (2011-2015)
GMC: Savana 2500/3500 Van (2016), Sierra 2500/3500 Pickup (2012-2016), Sierra Denali 2500 (2012-2015), Sierra Denali 3500 (2012-2016)
Frequently Asked Questions
Why do you need my VIN?
Your VIN is essential. It allows us to load the exact, correct GM software for your truck’s specific engine, transmission, and emissions equipment. This ensures perfect compatibility and performance, eliminating the need for further programming.
Is this a simple plug-and-play installation?
Yes, for most vehicles. Because the module is pre-programmed, you just need to install it. Some vehicles have an anti-theft system that may require a simple ‘relearn’ procedure after installation, which you can do yourself in about 30 minutes with just the ignition key.
Will this fix my specific problem?
This module is a direct solution for a failed ECM. If your vehicle displays common symptoms like processor fault codes (P0601, P0606), no-start conditions, or erratic behavior, and you have ruled out wiring or sensor issues, this part will resolve the issue.
What if I have a different part number on my old ECM?
This ECM replaces several part numbers, including 12668866, 12668994, and others listed above. As long as your vehicle is on the compatibility list, this module will function correctly once programmed to your VIN.
Do I need to return my old ECM?
There is no core charge for this part. You are not required to send your old, faulty module back to us.