Is Your Buick Lucerne Running Rough? The ECM Might Be the Culprit.
The Engine Control Module (ECM), often called the engine’s brain, is the master computer responsible for managing your 2009-2011 Buick Lucerne’s performance, fuel efficiency, and emissions. When it begins to fail, it can cause a cascade of confusing and frustrating problems, from a simple check engine light to a vehicle that won’t start at all. This replacement Engine Control Module, part number 12678512, is the definitive solution to restore your vehicle’s factory performance and reliability.
Unlike sourcing a module from a salvage yard or a big box store, this unit comes fully programmed to your vehicle’s specific Vehicle Identification Number (VIN). We flash it with the latest GM-certified software updates before it ships, ensuring it communicates perfectly with your car’s existing systems right out of the box. This critical step eliminates the need for an expensive trip to the dealership for programming, saving you both time and money.
From the Diagnostic Bay
We had a 2010 Lucerne come into the shop with a bizarre issue. The owner complained of intermittent stalling at stoplights and a transmission that seemed to shift harshly at random. There were no consistent trouble codes, just a generic U-code for lost communication every so often. We checked wiring, sensors, and even the transmission module. After hours of diagnostics, we decided to inspect the ECM. On a hunch, we swapped in a known-good, VIN-programmed module. The car immediately ran perfectly. The original ECM had an internal fault that was causing intermittent data corruption, creating ghost-like symptoms that were impossible to pin down. This is a classic example of how a failing 2009-2011 Lucerne ECM can manifest in ways that don’t point directly to the module itself.
Common Symptoms of a Failing 2009-2011 Lucerne ECM
- ✔ Check Engine Light: The most common indicator, often with codes related to sensors, communication, or processor faults.
- ✔ Engine Stalling or Misfiring: The ECM may fail to correctly time spark or fuel injection, leading to rough running, stalling, and poor acceleration.
- ✔ No-Start Condition: If the ECM cannot power up or communicate with the ignition and fuel systems, the engine will not start.
- ✔ Poor Fuel Economy: Incorrect air/fuel mixture calculations can cause a sudden and significant drop in MPG.
- ✔ Transmission Shifting Issues: The ECM works with the Transmission Control Module (TCM) to ensure smooth shifts. A faulty ECM can cause harsh shifting or failure to shift into certain gears.
- ✔ Intermittent Electrical Problems: Seemingly unrelated issues with cooling fans, gauges, or other electronic components can sometimes be traced back to a failing ECM.
A True Plug-and-Play Replacement
This isn’t just a part; it’s a comprehensive solution. By providing us with your VIN during checkout, you ensure that the module you receive is a perfect match for your vehicle’s specific configuration. It accounts for all factory options, emissions standards, and security protocols. The process is simple:
- Place your order for the 12678512 ECM.
- Provide your vehicle’s 17-digit VIN in the designated field or in a follow-up message.
- Our technicians will use professional equipment to flash the module with the correct, updated GM software.
- We ship the ready-to-install module directly to you.
In most cases, installation is straightforward, and after a simple security relearn procedure (often called a key relearn), your vehicle will be back on the road. This eliminates the hassle and high cost associated with dealership programming services.
Broad GM Compatibility
While this is a perfect fit for the 2009-2011 Lucerne ECM application, this versatile module (part number 12678512) is also a direct replacement for a wide range of other General Motors vehicles. It is fully interchangeable with the following service numbers: 12636659, 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, and 12630464. Please verify the part number on your original module or consult the detailed fitment list below to confirm compatibility with your specific make, model, and engine option.
Frequently Asked Questions
Why do you need my VIN?
Your VIN (Vehicle Identification Number) allows us to program the ECM with the exact software and calibrations for your car’s specific engine, transmission, and options. This ensures seamless integration and proper function without a trip to the dealer.
Is this a difficult part to install?
For the Buick Lucerne, the ECM is located in the lower part of the air cleaner box, making it relatively accessible. Installation typically involves disconnecting the battery, unplugging the electrical connectors, and unbolting the module. Most DIY mechanics with basic tools can perform the swap in under an hour.
Will I need to do anything after installing it?
Yes, you will likely need to perform a security relearn procedure, also known as a key relearn. This syncs the new ECM with your vehicle’s anti-theft system. The procedure is simple and can usually be done without special tools by following instructions included with the part or found online.
What if my original part number is different?
This module, 12678512, is the latest service replacement for several older part numbers, including 12636659, 12639300, and others listed in the description. As long as your original part number is on our interchange list, this module will work perfectly as a direct replacement.
Does this ECM come with a warranty?
Yes, all of our electronic modules come with a comprehensive warranty against defects in materials and workmanship. Please see the warranty tab on this page for specific details and duration.