Restore Peak Performance to Your 2018 Express 3500 Van
Is your work van or fleet vehicle suddenly unreliable? Experiencing a persistent check engine light, erratic engine behavior, or a no-start condition can bring your business to a halt. The Engine Control Module (ECM) is the brain of your vehicle’s powertrain, and when it fails, it can cause a host of frustrating and difficult-to-diagnose issues. This is a direct-fit, reliable solution for your 2018 Express 3500 ECM, designed to get you back on the road with confidence.
We take the guesswork out of the repair. Unlike a blank module from a dealer or a questionable part from a salvage yard, this ECM, part number 12704475, arrives at your door pre-programmed with the latest official GM software calibrations. All we need is your vehicle’s 17-digit Vehicle Identification Number (VIN) during checkout. This ensures the module is perfectly matched to your vehicle’s specific configuration, saving you a costly trip to the dealership for initial programming.
Case Study: A Tricky Diagnosis
I recently had a 2018 Savana 3500 in my bay with a classic intermittent no-start. The owner had already replaced the battery and starter. Scans showed a handful of communication codes (U-codes) but also a P0606 (ECM Processor Fault) that would pop up randomly. He had tried a used ECM from a junkyard, but the van wouldn’t even crank due to the immobilizer system mismatch. This is a common dead-end for modern vehicles. We ordered this exact VIN-programmed module. After installation, the van still wouldn’t start, which is expected. We performed the Security Relearn procedure using our shop’s Techline Connect subscription, and it fired right up. The P0606 code never returned. This highlights why starting with a correctly programmed module is the critical first step to a successful repair.
Common Signs of a Failing Engine Computer
- ✔ Check Engine Light is on with codes like P0601, P0606, or other internal processor faults.
- ✔ Vehicle will not start or has intermittent starting issues.
- ✔ Poor fuel economy and noticeable loss of power.
- ✔ Engine stalling, sputtering, or misfiring.
- ✔ Automatic transmission shifting erratically or harshly.
- ✔ Communication errors with other vehicle modules (U-codes).
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 reconnection.
- ✔ Locate the ECM: On the 2018 Express 3500 Van, the ECM is typically found in the left-hand rear of the engine compartment. Confirm its location before proceeding.
- ✔ Disconnect Connectors: Carefully release the locking tabs on the wiring harness connectors and gently pull them straight out from the module. Do not force them.
- ✔ Remove the Old Module: Unbolt the old ECM from its mounting bracket. Keep the mounting hardware, as you will need it for the new module.
- ✔ Install the New Module: Mount the new, pre-programmed ECM onto the bracket and secure it with the original hardware.
- ✔ Reconnect Everything: Firmly plug the wiring harnesses back into the new ECM until they click into place. Reconnect the negative battery terminal.
- ✔ Perform Relearn Procedures: The final, critical step. You will need to perform the vehicle’s security relearn procedure. If the vehicle does not start, this is a required step. Other procedures like a crankshaft variation relearn may also be necessary. This is the responsibility of the installer and requires a compatible professional scan tool or GM’s software (Tis2web/Techline Connect).
Verified Vehicle Compatibility
This ECM is a direct replacement for part number 12704475 and is also compatible with part numbers 12692069, 12680656, 12686383, and 12688528. It is confirmed to fit the following vehicles:
- 2018 Cadillac Escalade & Escalade ESV (Engine Compartment)
- 2018 Cadillac XTS (3.6L, VIN 8)
- 2018 Chevrolet Corvette (RH Cowl Under Dash)
- 2019 Chevrolet Corvette (VIN 6 – LT4 or VIN 7 – LT1)
- 2018 Chevrolet Express 2500/3500 Van (LH Rear Engine Compartment, 4.3L)
- 2018 Chevrolet Silverado 1500 (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 (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
Frequently Asked Questions
Do I need to get this programmed?
No, the initial programming is done by us before shipping. We flash it with the latest GM software using the VIN you provide. However, you will need to perform on-vehicle relearn procedures after installation.
What is the security relearn procedure?
This is a process that syncs the new ECM to your vehicle’s anti-theft system (immobilizer). If it’s not performed, the vehicle will not start. This procedure requires a professional scan tool or access to GM’s Tis2web/Techline Connect software and is the responsibility of the installer.
What if I don’t provide my VIN?
We cannot ship the module without your VIN. The programming process is essential for the part to function correctly in your specific vehicle. Please provide your VIN at checkout to avoid delays.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the old ECM (e.g., codes P0601, P0606), then yes, this part is the correct fix. However, if the light is on for other reasons (like a bad sensor), you must fix that underlying issue first.
Where is the ECM located on my 2018 Express Van?
On the 2018 Express and Savana vans with the 4.3L engine, the Engine Control Module is located in the engine compartment, on the left-hand (driver’s side) rear area.