Is your 2018 Savana 3500 Van running rough, stalling, or throwing a persistent Check Engine light? You’re not just dealing with an annoyance; you’re facing a potential failure of the vehicle’s brain—the Engine Control Module (ECM). As a technician with over two decades of experience, I’ve seen firsthand how a faulty ECM can cause a cascade of frustrating, hard-to-diagnose issues. This isn’t just a part; it’s the central command for your engine’s performance, fuel efficiency, and reliability.
We offer a straightforward, reliable solution: a genuine GM Engine Control Module, part number 12704475, delivered to your door already programmed with the latest GM software updates for your specific vehicle. Simply provide your Vehicle Identification Number (VIN) after purchase, and our experts will handle the programming. This critical step ensures the module communicates perfectly with your van’s systems right out of the box, saving you a costly trip to the dealership for programming.
Case Study: A Tricky Diagnosis
I remember a 2018 Express van from a local plumbing company that came into my shop. The driver complained about intermittent stalling at stoplights and a transmission that seemed to shift at the wrong times. They had already replaced the throttle body and a few sensors with no luck. After hooking up my scan tool, I saw no hard codes, just some confusing data streams. Experience told me to look at the core system. We swapped in one of our pre-programmed ECMs, performed the quick security relearn, and the van ran perfectly. The original ECM had an internal processor fault that only acted up under specific thermal conditions. This replacement saved them from chasing phantom issues and got their work van back on the road earning money.
Is Your Vehicle Showing These Telltale ECM Failure Signs?
A failing ECM can manifest in various ways. If you’re experiencing any of the following, it’s a strong indicator that your engine computer may be the culprit.
- ✔ Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (ECM/PCM Processor Fault).
- ✔ The engine cranks but refuses to start.
- ✔ Noticeable drop in fuel economy.
- ✔ Rough idling, stalling, or hesitation during acceleration.
- ✔ Automatic transmission shifting erratically or harshly.
- ✔ Communication errors with other vehicle modules (U-codes).
Your Guide to a Smooth Installation
Replacing the 2018 Savana 3500 ECM is a manageable job for a confident DIYer or any professional technician. Following these steps will ensure a successful repair.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- Locate the ECM: On the Savana/Express vans, the ECM is typically found in the left rear of the engine compartment. Consult a service manual for your specific vehicle if you’re unsure.
- Disconnect and Remove: Carefully unplug the wiring harness 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 your new, pre-programmed ECM securely onto the bracket and reconnect the wiring harnesses. Ensure they click firmly into place.
- Reconnect the Battery: Reattach the negative battery terminal.
- Perform Security Relearn: In many cases, the vehicle will start right up. However, if it doesn’t, a Vehicle Theft Deterrent (VTD) relearn is necessary. This procedure requires a compatible professional scan tool or access to GM’s TIS2WEB/Techline Connect system and is the responsibility of the installer.
- Additional Procedures: Depending on your vehicle, other relearns like a crankshaft position variation relearn may be needed to achieve optimal performance.
Will This Fit My Vehicle?
This module is a direct-fit replacement for a wide range of GM vehicles. While we are focusing on the 2018 Savana 3500 ECM, please verify your part number. This unit, 12704475, also replaces part numbers 12692069, 12680656, 12686383, and 12688528. It is compatible with the following models and options:
- 2018-2019 Corvette: (RH cowl under dash)
- 2018 Cadillac Escalade / Escalade ESV: (Engine compartment)
- 2018 Cadillac XTS: (3.6L, VIN 8 – opt LF3)
- 2018 Chevrolet Express 2500/3500 Van: (LH rear engine compartment), 4.3L
- 2018 Chevrolet Silverado 1500 Pickup: (LH front engine compartment), ID 12680656
- 2018 Chevrolet Suburban 1500: (LH front engine compartment)
- 2018 Chevrolet Tahoe: (LH front engine compartment)
- 2018 GMC Savana 2500/3500 Van: (LH rear engine compartment), 4.3L
- 2018 GMC Sierra 1500 Pickup: (LH front engine compartment), ID 12680656
- 2018 GMC Sierra Denali 1500: (LH front engine compartment), ID 12686383
- 2018 GMC Yukon / Yukon XL 1500: (LH front engine compartment)
Frequently Asked Questions
What does ‘VIN Programmed’ mean?
It means we load the module with the specific factory software for your exact vehicle using your VIN. This ensures all systems, from the engine to the transmission, operate according to GM’s original specifications for your van.
How do I provide my VIN?
After you complete your purchase, you will receive instructions on how to send us your 17-digit VIN. We cannot ship the part until we have this information to program it correctly.
What is the ‘theft relearn’ and why is it my responsibility?
The Vehicle Theft Deterrent (VTD) system links your ECM to your keys and other modules. When you install a new ECM, this link must be re-established. It’s an on-vehicle security procedure that requires specific tools (like GM’s Techline Connect) that we cannot perform remotely. It is a standard final step for this type of repair.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of your old ECM (like codes P0601-P0606), then yes, this part will resolve the issue. However, if the light is on due to a bad sensor or other mechanical problem, you will still need to fix that underlying issue.
Do I need to send my old ECM back?
No core charge or return is required for this part. You can keep or responsibly dispose of your old module.