Is Your Sierra 3500 Sidelined with Engine Problems?
There’s nothing more frustrating than when your workhorse truck is down. If your 2012-2016 Sierra 3500 is experiencing baffling issues like intermittent stalling, a no-start condition, erratic shifting, or a check engine light that won’t go away, the Engine Control Module (ECM) is a highly likely culprit. As the central computer for your powertrain, its failure can cause a cascade of problems that are often misdiagnosed, costing you time and money on unnecessary parts.
Just last month, a 2014 Sierra 3500 with the 6.0L gas engine was towed into my shop. The owner was at his wit’s end dealing with a persistent U0100 ‘Lost Communication with ECM/PCM’ code and random power loss under load. We spent an hour verifying the main power and ground circuits and checking the data bus wiring for integrityโall were solid. The issue, as I’ve seen on dozens of these GM trucks, was an internal failure within the original ECM. Heat, vibration, and age had taken their toll on the delicate internal circuitry.
The Direct-Fit, Programmed Solution
This isn’t just a replacement part; it’s a complete solution. This Engine Control Module (part number 12668991) is the answer to getting your truck back on the road reliably and quickly. The most significant benefit is our professional programming service. Before we ship the module, we use your truck’s Vehicle Identification Number (VIN) to flash it with the latest, most stable GM-approved software. This critical step ensures the ECM is perfectly matched to your truck’s specific engine, transmission, and factory options, eliminating the need for expensive dealer programming.
Symptoms of a Failing 2012-2016 Sierra 3500 ECM:
- โ Persistent Check Engine Light (CEL)
- โ Communication error codes (U-codes) stored in other modules
- โ Engine cranks but will not start
- โ Unexplained stalling or rough idling
- โ Noticeable decrease in fuel economy
- โ Harsh or delayed transmission shifting
- โ Reduced engine power or sluggish acceleration
Expert Pro Tip: Check Your Connectors First
Before installing your new module, take 60 seconds to inspect the vehicle’s harness connectors. Over time, the female pins can spread apart, creating a weak connection that can mimic ECM failure. Use a small pick to gently check for proper tension on the pins. Cleaning the connectors with a dedicated electronics contact cleaner is also a great preventative measure to ensure a solid, long-lasting connection.
Plug-and-Play Installation: No Dealer Visit Required
Installing this module is a straightforward process you can do in your own driveway. By ordering a pre-programmed unit, you bypass the hassle and expense of towing your truck to a dealership. Follow these general steps to get your Sierra running right:
- Safety First: Disconnect the negative terminal from your truck’s battery.
- Locate the ECM: On the Sierra 3500, the ECM is typically found in the left-front of the engine compartment, near the battery or air filter housing.
- Disconnect: Carefully unlatch and remove the electrical connectors. Avoid forcing them.
- Unbolt and Remove: Remove the mounting bolts holding the old ECM in place and take it out.
- Install the New Module: Seat the new ECM in the mounting bracket and secure it with the bolts.
- Reconnect: Firmly plug the harness connectors into the new module until they click into place. Reconnect the battery terminal.
- Final Steps: In some cases, a security relearn procedure (often called a Passlock or anti-theft relearn) may be required. This can typically be done without special tools and involves a sequence of key cycles. Instructions are widely available online for your specific model year.
Guaranteed Compatibility
This ECM is a direct replacement for a wide range of GM vehicles and is interchangeable with several part numbers. Please verify your original part number or use the fitment guide to ensure this is the correct component for your vehicle.
Replaces Part Numbers: 12668866, 12668994, 12643636, 12663405, 12670335, 22819494, 12692200
Fits Select Models Including:
- 2012-2016 Sierra / Silverado 2500 & 3500 (6.0L)
- 2016 Express / Savana 2500 & 3500 Vans (4.8L, 6.0L)
- 2011-2016 Chevrolet Volt, Cruze, Sonic, Trax
- 2013-2016 Buick Encore
- And more… (Check the full fitment list)