Restore Peak Performance to Your GM Truck
Is your Sierra Denali 2500 suffering from frustrating issues like a persistent check engine light, erratic engine behavior, stalling, or a complete no-start condition? These are classic signs of a failing Engine Control Module (ECM), the electronic brain of your vehicle. In my 20+ years of hands-on diagnostics, I’ve seen how a faulty ECM can cripple even the most powerful trucks, causing everything from poor fuel economy to leaving you stranded. This isn’t just an inconvenience; for a workhorse like the Sierra HD, it’s a critical failure that costs you time and money.
This replacement Engine Control Module, part number 12670335, is the definitive solution. We take the guesswork and dealer hassle out of the equation. Before we ship this module to you, our technicians will program it with the latest official GM software updates, specifically matched to your truck using its unique Vehicle Identification Number (VIN). This ensures seamless communication with all other vehicle systems and restores the precise engine management your truck had when it left the factory.
A Technician’s Notebook
I remember a 2014 Silverado 2500 with the 6.0L V8 (which uses this exact ECM) that came into the shop with a bizarre, intermittent no-crank/no-start issue. The owner had already replaced the battery and starter. We scanned it and found no communication codes. All the power and ground feeds to the ECM were perfect. After hours of tracing wires, we monitored the ECM’s internal processor activity on an advanced scope. We discovered the processor would randomly drop out under certain temperature conditions—a problem impossible to see with a standard scan tool. Replacing the ECM with a properly programmed unit like this one solved the problem instantly. It’s a reminder that sometimes the ‘brain’ itself is the issue, even when it’s not throwing obvious codes.
Is Your Truck Showing These Signs of a Bad ECM?
- âś” Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (ECM/PCM Processor Fault).
- âś” Engine cranks but will not start.
- âś” Unexplained drop in fuel efficiency.
- âś” Rough or unstable idle.
- âś” Engine stalling or hesitating during acceleration.
- âś” Loss of communication with the scan tool.
- âś” Harsh or incorrect shifting from the transmission.
A Straightforward Guide to Installation
Installing your new 2012-2016 Sierra Denali 2500 ECM is a manageable job for a confident DIYer or any professional mechanic. Since we program it beforehand, no additional on-vehicle procedures are typically required.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the ECM: On most 2012-2016 GM HD trucks, the ECM is located on the driver’s side of the engine compartment, near the firewall or inner fender.
- Disconnect the Harnesses: Carefully release the locking tabs on the electrical connectors and pull them straight out from the module. Do not force them. Inspect the connectors for any corrosion or damaged pins.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the hardware as you will need it for the new unit.
- Install the New Module: Mount the new ECM onto the bracket and secure it with the original hardware.
- Reconnect Everything: Plug the electrical harnesses back into the new ECM until they click securely into place. Reconnect the negative battery terminal.
- Final Check: Turn the key to the ‘On’ position for 10-15 seconds before starting the engine. This allows all the vehicle’s systems to recognize the new module. Start your engine and check for proper operation.
Verified Vehicle Compatibility
This ECM is a direct-fit replacement for a wide range of General Motors vehicles. While this listing focuses on the 2012-2016 Sierra Denali 2500 ECM, it is also compatible with numerous other models. Please verify your part number or consult the list below. This module replaces part numbers: 12668866, 12668994, 12643636, 12663405, 12670335, 22819494, and 12692200.
- GMC Sierra 2500/3500 HD (2012-2016) w/ 6.0L Gas Engine
- Chevrolet Silverado 2500/3500 HD (2012-2016) w/ 6.0L Gas Engine
- GMC Savana / Chevrolet Express 2500/3500 (2016) w/ 4.8L or 6.0L Gas Engine
- Chevrolet Cruze (2012-2016)
- Chevrolet Sonic (2012-2016)
- Buick Encore (2013-2016)
- Chevrolet Trax (2013-2016)
- And many other models as detailed in the full fitment data.
Frequently Asked Questions
Do I need to get this ECM programmed by a dealer?
No. We handle the programming for you before shipment. Simply provide your vehicle’s VIN during checkout, and it will arrive ready to install. This saves you the time, cost, and hassle of a dealership visit.
What is a VIN and where do I find it?
The VIN (Vehicle Identification Number) is your car’s unique 17-digit serial number. You can find it on your vehicle’s registration, insurance card, or on a small plate on the driver’s side of the dashboard, visible through the windshield.
Will this fix my specific problem or check engine light?
This module will correct issues directly caused by a faulty ECM. If your vehicle has been properly diagnosed with a failed ECM (e.g., codes P0601, P0606), this part is the solution. However, it will not fix problems related to other faulty components like sensors or wiring.
How do I know if this part number will fit my vehicle?
This ECM, 12670335, replaces several earlier part numbers. The best way to ensure compatibility is to match the part number from your original module. If you’re unsure, check our detailed fitment list or contact us with your VIN, and we can verify it for you.
What is the difference between an ECM and a PCM?
The terms are often used interchangeably. ECM stands for Engine Control Module, while PCM means Powertrain Control Module. A PCM controls both the engine and transmission, while an ECM typically just controls the engine. In modern vehicles like your Sierra, this single unit often functions as the PCM.