Restore Peak Performance to Your Workhorse Van
If your 2016 Express 3500 Van is struggling with erratic behavior—like rough idling, stalling, poor fuel economy, or a persistent Check Engine Light—the root cause is often a failing Engine Control Module (ECM). As the central computer of your vehicle, a faulty ECM can create a cascade of frustrating and difficult-to-diagnose issues. This isn’t just an inconvenience; for a work van, it means downtime and lost revenue. This replacement 2016 Express 3500 Engine Control Module is the reliable, straightforward solution to get your vehicle back in service and operating as it should.
We take the guesswork and hassle out of the repair. Unlike sourcing a part from a salvage yard that requires expensive dealership tools for programming, this module arrives at your door ready for installation. Simply provide us with your vehicle’s VIN during checkout, and our technicians will flash the unit with the latest, most stable software directly from GM. This ensures perfect compatibility and resolves many underlying issues that older software versions may have had.
A Technician’s Notebook: The Intermittent No-Start
I had a 2016 Express 3500 from a local plumbing company towed to my bay. The complaint was intermittent no-starts and random stalling, but no consistent trouble codes. The driver was losing time and money. After checking all the basics—battery, alternator, fuel pressure—everything seemed fine. On a hunch, I monitored the 5-volt reference signal from the ECM to various sensors. I noticed it would occasionally drop out, causing the engine to stumble or refuse to start. This is a classic internal ECM failure. We installed a VIN-programmed module like this one, and the van has been running reliably for them ever since. It’s often these ghost-in-the-machine problems that point directly to the vehicle’s computer.
Is Your Express Van Showing These Symptoms?
A failing ECM can manifest in numerous ways. If you’re experiencing any of the following, this module is the likely fix you need. Cross-reference these symptoms and common Diagnostic Trouble Codes (DTCs) with your own diagnostics.
- ✔ Check Engine Light is on with codes like P0601, P0602, P0606 (Internal Control Module Processor Error).
- ✔ Unexplained engine misfires, stumbling, or hesitation during acceleration.
- ✔ The engine cranks but refuses to start (intermittent or total no-start).
- ✔ Noticeable decrease in fuel efficiency.
- ✔ Problems with the automatic transmission, such as harsh or erratic shifting.
- ✔ Communication errors with scan tools (e.g., U0100 – Lost Communication With ECM/PCM).
- ✔ Failure to pass state emissions testing.
A Straightforward Guide to Installation
Installing your new 2016 Express 3500 Engine Control Module is a manageable job for a DIYer with basic tools. While this unit is pre-programmed, some vehicles may require a security or crankshaft position sensor relearn procedure, which can be done with many professional-grade scan tools or by following specific vehicle procedures.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait at least 10 minutes for capacitors to discharge.
- Locate the ECM: On the Express/Savana van, the ECM is typically found in the left-hand rear of the engine compartment.
- Disconnect Connectors: Carefully release the locking tabs on the wiring harness connectors and pull them straight out from the module. 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 Module: Mount the new ECM securely onto the bracket and re-tighten the bolts.
- Reconnect Everything: Plug the wiring harnesses back into the new ECM until they click firmly into place. Reconnect the negative battery terminal.
- Final Steps: Turn the key to the ‘ON’ position (without starting) for 10-15 seconds to allow the system to initialize. Start the vehicle. A security or CASE relearn may be necessary if indicated by a security light or certain trouble codes.
Verified Compatibility for Your GM Vehicle
This module is a direct replacement for part number 12668866 and is interchangeable with several other part numbers. Please confirm your vehicle is on this list. This unit is guaranteed to fit and function correctly in the following models:
- Buick Encore: 2013-2016 (1.4L)
- Cadillac ELR: 2014-2016
- Chevrolet Cruze: 2012-2016 (Gasoline, incl. Limited)
- Chevrolet Express 2500/3500 Van: 2016 (4.8L, 6.0L)
- Chevrolet Silverado 2500/3500 Pickup: 2012-2016 (6.0L)
- Chevrolet Sonic: 2012-2016
- Chevrolet Spark: 2014-2015 (Gasoline)
- Chevrolet Suburban 3500: 2016
- Chevrolet Trax: 2013-2016
- Chevrolet Volt: 2011-2015
- GMC Savana 2500/3500 Van: 2016 (4.8L, 6.0L)
- GMC Sierra 2500/3500 Pickup (incl. Denali): 2012-2016 (6.0L)
Yes, absolutely. Providing your VIN is critical. We use it to load the precise, factory-correct software for your vehicle’s specific configuration, including engine, transmission, and emissions equipment. This ensures a seamless installation and proper function.
For most vehicles, yes. Because we program it to your VIN, it eliminates the need for dealer programming. However, some GM vehicles may require a security relearn or a Crankshaft Variation (CASE) relearn procedure after installation, which can be completed with a capable bidirectional scan tool.
It very well could. The ECM (often called a PCM when it controls both engine and transmission) is responsible for interpreting sensor data to command gear shifts. If the module is faulty, it can cause harsh shifting, delayed engagement, or incorrect gear selection. Replacing a bad ECM often resolves these issues.
This module replaces multiple GM part numbers, including 12668994, 12643636, 12663405, and others listed in our fitment data. As long as your vehicle model and year are listed, and you provide a valid VIN, this module will function correctly as a replacement.
Yes, all our electronic modules come with a warranty. Please refer to the warranty information tab on this page for specific details and duration of coverage for your peace of mind.