Restore Your GM Vehicle’s Core Performance
Is your work van, truck, or performance car suddenly unreliable? A faulty Engine Control Module (ECM) is often the culprit behind a host of frustrating and hard-to-diagnose issues. From a vehicle that refuses to start to unexplained check engine lights and poor fuel economy, a failing ECM can bring your daily operations to a halt. This isn’t just an inconvenience; it’s a direct hit to your productivity and peace of mind. This replacement ECM, part number 12704475, is the definitive solution, engineered to restore your vehicle’s factory performance and reliability.
We take the guesswork and dealer-dependency out of the equation. Before we ship your part, we flash it with the latest, most stable GM factory software calibrations, specifically matched to your vehicle using the VIN you provide. This ensures that the module you receive is ready for installation and prepared to communicate correctly with your vehicle’s other systems. This service saves you a costly trip to the dealership and significant diagnostic time, getting you or your customer back on the road faster.
A Technician’s Notebook: The Intermittent No-Start Fleet Van
I once had a 2018 Savana 3500 from a local plumbing company in my bay. The complaint was maddening: intermittent no-start. It would work perfectly for a week, then leave a technician stranded. No specific codes were stored consistently, just a few random U-codes (loss of communication) that would clear. After checking grounds, power feeds, and the CAN bus network for the third time, I focused on the ECM. On a hunch, I monitored the 5-volt reference signal from the ECM to various sensors during a wiggle test of the main harness. Sure enough, a slight movement near the ECM connector caused the voltage to drop out, killing the engine. The internal board of the original ECM had developed a micro-fracture. Swapping in a properly programmed module like this one provided a permanent fix, and that van has been the most reliable in their fleet ever since.
Common Symptoms of a Failing GM ECM
If the brain of your engine is failing, you’ll notice it. I’ve seen hundreds of these cases in my shop. Keep an eye out for these tell-tale signs that point to a needed 2018 Savana 3500 ECM replacement:
- ✔ Complete no-start or crank-no-start condition.
- ✔ Check Engine Light is on with communication-related Diagnostic Trouble Codes (DTCs) like U0100.
- ✔ Poor or erratic automatic transmission shifting.
- ✔ A noticeable drop in fuel efficiency for no apparent reason.
- ✔ Engine stalling, sputtering, or misfiring intermittently.
- ✔ Issues with other modules, as the ECM is a central communication hub.
A Straightforward Guide to Installation
Replacing the ECM is a manageable job for a DIY enthusiast or a quick task for a professional. The most critical part is ensuring the post-installation procedures are completed.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts.
- Locate the ECM: On the Savana/Express vans, it’s typically found in the LH rear of the engine compartment. On trucks and SUVs, it’s often on the LH front of the engine compartment. Consult a service manual for your specific vehicle’s location.
- Disconnect and Remove: Carefully unplug the electrical connectors. They have locking tabs that need to be released. Once disconnected, unbolt the old ECM from its mounting bracket.
- Install the New ECM: Mount the new module securely onto the bracket and reconnect the electrical harnesses. Ensure they click into place. Reconnect the battery terminal.
- CRITICAL – Perform Relearn Procedures: Turn the key to the ‘ON’ position. If the vehicle does not start, you must perform a Vehicle Theft Deterrent System relearn using a GM-compliant scan tool with access to TIS2WEB or Techline Connect. Depending on your vehicle, you may also need to perform a Crankshaft Position Variation relearn or other setup procedures. This is the responsibility of the installer.
Will This Fit My Vehicle?
This module is a direct replacement for multiple part numbers and fits a wide range of GM vehicles. Please verify your model and options below. This part replaces numbers 12704475, 12692069, 12680656, 12686383, and 12688528.
- 2018 Cadillac Escalade & Escalade ESV
- 2018-2019 Chevrolet Corvette (verify engine option)
- 2018 Chevrolet Express 2500/3500 Van (with 4.3L engine)
- 2018 Chevrolet Silverado 1500 Pickup (verify ID 12680656)
- 2018 Chevrolet Suburban 1500
- 2018 Chevrolet Tahoe
- 2018 GMC Savana 2500/3500 Van (with 4.3L engine)
- 2018 GMC Sierra 1500 Pickup (verify ID 12680656)
- 2018 GMC Sierra Denali 1500 (verify ID 12686383)
- 2018 GMC Yukon & Yukon XL 1500
- 2018 Cadillac XTS (with 3.6L, VIN 8, opt LF3)
Frequently Asked Questions
Do I really need to provide my VIN?
Do I really need to provide my VIN?
Yes, it is absolutely essential. We use your Vehicle Identification Number (VIN) to load the precise, vehicle-specific GM software and calibrations onto the ECM before shipping. This ensures compatibility and proper engine function.
What is a ‘theft relearn’ and can I do it myself?
The theft deterrent relearn synchronizes the new ECM with your vehicle’s security system. If it’s not done, the vehicle will not start. This procedure requires a professional scan tool with access to GM’s software (like Techline Connect). It is not possible with a basic code reader.
My original part number is 12692069. Will this part work?
Yes. This ECM, part number 12704475, is the updated, correct service replacement for several older part numbers, including 12692069. It will fit and function correctly in its place.
What if I install it and the vehicle still has problems?
First, confirm that all required relearn procedures (theft, crankshaft variation, etc.) have been successfully completed by a qualified technician. If problems persist, the issue may lie with other components like wiring, sensors, or grounds. A faulty ECM is a common issue, but it’s important to ensure the root cause was correctly diagnosed.