Restore Your Truck’s Brain and Get Back on the Road
Is your 2017-2018 Sierra Denali 1500 suffering from baffling issues like stalling, erratic shifting, a persistent check engine light, or a complete no-start condition? The Engine Control Module (ECM) is the central computer of your vehicle, and when it fails, it can cause a host of frustrating and performance-robbing problems. This isn’t just an inconvenience; it’s a critical failure that compromises your truck’s reliability. This replacement ECM, part number 12678815, is the definitive solution to restore your vehicle’s factory performance and dependability.
We take the biggest hassle out of the replacement process. Before this module ships, we program it with the latest official GM software calibrations specifically for your truck using the VIN you provide. This ensures perfect communication between the engine, transmission, and other vehicle systems, right out of the box. You get a component that is ready for the final on-vehicle learning procedures, saving you a costly and time-consuming trip to the dealership for initial programming.
A Technician’s Notebook: The Intermittent Stall
A customer brought in his ’17 Sierra Denali with a problem that had two other shops stumped: it would randomly stall at stoplights, but not every time. No consistent codes were stored, just a history of U0100 (Lost Communication with ECM). After hours of checking wiring harnesses and grounds, we monitored live data. We noticed the 5-volt reference signal from the ECM would momentarily drop just before a stall. This tiny fluctuation pointed directly to an internal fault in the module. We installed one of our VIN-programmed ECMs, performed the crankshaft variation and theft relearns, and the problem was gone for good. It’s a classic example of how a failing 2017-2018 Sierra Denali ECM can create ghost-like issues that are impossible to trace without replacing the faulty component.
Is Your Truck Showing These Symptoms?
- ✔ Check Engine Light is on with codes like P0601, P0606, or U0100.
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained drops in fuel economy.
- ✔ Rough or unstable idling.
- ✔ The vehicle stalls unexpectedly while driving or at a stop.
- ✔ Hesitation or stumbling during acceleration.
- ✔ Transmission shifting feels harsh or erratic.
Your Straightforward Installation Guide
Replacing the ECM is a manageable task for a confident DIYer or any professional technician. Follow these steps for a successful installation.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts.
- Locate the ECM: On most GM trucks like the Sierra, the ECM is found in the engine compartment, typically on the driver’s side near the firewall or fender.
- Disconnect Connectors: Carefully release the locking tabs and unplug the large 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 and remove it from the vehicle.
- Install the New ECM: Mount your new, pre-programmed ECM onto the bracket and securely plug in the wiring harness connectors. You should hear a ‘click’ as they lock into place.
- Reconnect Battery: Re-attach the negative battery terminal.
- Perform Relearn Procedures: This is a critical step. The vehicle may not start until a Vehicle Theft Deterrent (VTD) relearn is completed using a capable scan tool or GM’s TIS2Web/Techline Connect software. Other procedures like the crankshaft position variation relearn may also be required. This final step is the responsibility of the installer.
Verified Vehicle Compatibility
This module is a direct replacement for part number 12678815 and is interchangeable with 12692068, 12704476, 12686382, 12674052, and 12674472. It is guaranteed to fit the following models:
- 2017 Cadillac Escalade & Escalade ESV
- 2017 Cadillac XTS (3.6L Twin Turbo, VIN 8)
- 2017 Cadillac CTS (6.2L Supercharged or 3.6L Twin Turbo)
- 2017 Cadillac ATS (3.6L, VIN Y)
- 2017 Chevrolet Corvette
- 2017 Chevrolet Tahoe & Suburban 1500
- 2016-2018 Chevrolet Silverado 1500
- 2017-2018 GMC Yukon & Yukon XL 1500
- 2016-2018 GMC Sierra 1500
- 2017-2018 GMC Sierra Denali 1500
Why do you need my VIN?
Why do you need my VIN?
Your Vehicle Identification Number (VIN) is essential for us to load the exact, correct GM factory software for your truck’s specific engine, transmission, and emissions equipment. This pre-programming step ensures the module works correctly upon installation and is a service that saves you a trip to the dealer.
What is a ‘theft relearn’ and do I have to do it?
Yes, this is a mandatory step for the installer. The Vehicle Theft Deterrent (VTD) system links your key and ignition to the ECM. When you install a new ECM, the system sees it as a potential theft and prevents the engine from starting. A relearn procedure, performed with a professional scan tool or GM software, re-establishes this security link. This is the responsibility of the buyer/installer.
Will this fix my check engine light?
If your check engine light is caused by an internal failure of the old ECM (common codes P0601-P0606), then this replacement 2017-2018 Sierra Denali ECM will resolve the issue after installation and clearing of codes. However, if the light is on for another reason (e.g., a bad oxygen sensor), you will still need to fix that separate problem.
Is this a simple plug-and-play part?
It is ‘plug-in’ and pre-programmed, but not fully ‘play’. The physical installation is straightforward, but the required post-installation relearn procedures (like the theft and crankshaft variation relearns) require specific tools and knowledge. We recommend installation by a professional mechanic or an advanced DIYer who has access to GM’s Techline Connect or an equivalent high-level diagnostic tool.