Restore Peak Performance to Your GM Truck or SUV
Is your 2018 Sierra 1500, Silverado, or other compatible GM vehicle plagued by frustrating engine problems? A faulty Engine Control Module (ECM) is often the hidden culprit behind issues that seem impossible to pin down. As a technician with over two decades of experience, I’ve seen firsthand how a failing ECM can mimic a dozen other problems, leading to wasted time and money on incorrect repairs. This replacement ECM, part number 12704475 (interchangeable with 12680656, 12692069, 12686383, and 12688528), is the definitive solution to get your vehicle running like new again.
We take the guesswork and dealership hassle out of the equation. Before this module ships, we program it using your vehicle’s specific VIN. This ensures it has the latest, most stable software updates from General Motors, tailored precisely for your engine and transmission combination. This isn’t a generic, one-size-fits-all part; it’s a component prepared for your exact vehicle, ensuring optimal fuel economy, emissions compliance, and engine performance right out of the box.
Is Your Vehicle Showing These Symptoms?
- ✔ Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error) or U0100 (Lost Communication with ECM).
- ✔ The engine cranks but refuses to start, or starts and immediately stalls.
- ✔ Unexplained drops in fuel mileage and poor engine performance.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Intermittent stalling, especially when coming to a stop or at idle.
- ✔ Communication issues with diagnostic scan tools.
A Technician’s Notebook: The Intermittent No-Start
A customer brought in a 2018 Sierra 1500 that would randomly refuse to start. No crank, no click—just silence. Other times, it ran perfectly. The battery, starter, and relays all tested fine. After hours of chasing wires, we noticed that when the no-start occurred, our high-end scan tool couldn’t communicate with the engine computer. That was the key. The ECM was intermittently failing internally, dropping off the vehicle’s data network. We installed a VIN-programmed 2018 Sierra 1500 ECM, performed the security relearn, and the problem was solved for good. It’s a classic example of how the ECM can be the root cause of baffling electronic issues.
A Straightforward Guide to Installation
- ✔ Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental contact.
- ✔ Locate the ECM: On the 2018 Sierra/Silverado 1500, the ECM is typically found in the left (driver’s side) front of the engine compartment. Consult a service manual if you are unsure of the location on your specific model.
- ✔ Disconnect Connectors: Carefully release the locking tabs on the electrical wiring harnesses and disconnect them from the old ECM. Avoid pulling on the wires themselves.
- ✔ Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the hardware as you will need it for the new module.
- ✔ Install the New ECM: Mount your new, pre-programmed ECM onto the bracket and secure it with the original hardware.
- ✔ Reconnect Everything: Plug the wiring harnesses back into the new ECM, ensuring they click securely into place. Reconnect the negative battery terminal.
- ✔ Perform Relearn Procedures: The final, critical step. You will likely need to perform a Vehicle Theft Deterrent System (VTDS) relearn. If the vehicle does not start, this is the reason. This procedure requires a GM-compatible scan tool with access to TIS2Web or Techline Connect. Other relearns, like for the crankshaft position sensor, may also be necessary.
Will This Fit My Vehicle?
This module is verified to fit the following makes and models. Please match your part number (12680656, 12704475, 12692069, 12686383, 12688528) or vehicle application for guaranteed compatibility.
- 2018 Cadillac Escalade & Escalade ESV
- 2018-2019 Chevrolet Corvette (various engines)
- 2018 Chevrolet Express 2500/3500 Van (4.3L)
- 2018 Chevrolet Silverado 1500 Pickup (ID 12680656)
- 2018 Chevrolet Suburban 1500
- 2018 Chevrolet Tahoe
- 2018 GMC Savana 2500/3500 Van (4.3L)
- 2018 GMC Sierra 1500 Pickup (ID 12680656)
- 2018 GMC Sierra Denali 1500 (ID 12686383)
- 2018 GMC Yukon & Yukon XL 1500
- 2018 Cadillac XTS (3.6L, VIN 8)
Frequently Asked Questions
Frequently Asked Questions
How do I provide my VIN for programming?
After you complete your purchase, simply send us a message with your 17-digit Vehicle Identification Number (VIN). We cannot program and ship your module without it.
What is a theft deterrent relearn and why is it necessary?
It’s a security procedure that syncs the new ECM to your vehicle’s anti-theft system and ignition keys. Without this step, the system will assume a theft is in progress and prevent the engine from starting. This is a standard procedure for modern GM vehicles.
Can I perform the theft relearn myself?
Performing the theft relearn requires a professional-grade scan tool with access to GM’s software (TIS2Web/Techline Connect). While some advanced DIYers may have this, most customers will need to have a local repair shop or mobile technician perform this final step after installation.
What happens if I install it and the truck doesn’t start?
This is the exact symptom of needing the theft deterrent relearn. The module is programmed correctly for engine operation, but it needs to be introduced to your vehicle’s security system before it will allow the engine to run.
Is this part number 12680656 compatible with other numbers?
Yes. This module, service part number 12704475, is the correct, updated replacement for several older part numbers, including 12680656, 12692069, 12686383, and 12688528.