Restore Peak Performance to Your GM Vehicle
As a technician with over two decades of experience under the hood, I’ve seen firsthand how a failing Engine Control Module (ECM) can turn a reliable vehicle into a source of constant frustration. The ECM is the brain of your engine, managing everything from fuel mixture and ignition timing to transmission shifting and emissions. When it starts to fail, you’re often left with baffling symptoms that can be difficult to diagnose. This isn’t just a replacement part; it’s a complete, reliable solution for your vehicle’s electronic heart.
This ECM, part number 12636659, is the definitive fix for a wide range of GM vehicles, including the 2009-2011 Buick Lucerne. The biggest challenge with ECM replacement has always been the programming. Dealerships charge a small fortune, and most local shops don’t have the specific equipment. We solve that problem for you. Before this module ships, we flash it with the latest official GM software, perfectly matched to your vehicle’s VIN. This means it arrives at your door ready for a straightforward installation, getting you back on the road without the extra cost and hassle of a dealer visit.
A Technician’s Notebook: The Intermittent Stall Case
I remember a 2010 Lucerne that came into the bay with a complaint that stumped two other shops: it would stall randomly at stoplights, but only when the engine was hot. There were no consistent trouble codes, just a history of random communication errors. The owner had already replaced the fuel pump and cleaned the throttle body to no avail. After hooking up my diagnostic scanner and monitoring live data, I noticed the short-term fuel trim values would suddenly go erratic just before a stall. This pointed away from a mechanical issue and straight to the processor. The original ECM’s internal circuits were failing under heat soak. We installed a VIN-programmed 2009-2011 Lucerne ECM, and the problem was solved instantly. It’s a classic case of how a failing computer can mimic a fuel or air delivery problem.
Common Signs of a Failing Engine Computer
If your vehicle is experiencing any of the following, a faulty ECM could be the culprit. I’ve seen these symptoms in my shop countless times.
- ✔ Check Engine Light is on with codes like P0601, P0606 (Internal Control Module Processor Error), or U0100 (Lost Communication With ECM/PCM).
- ✔ The engine cranks but refuses to start.
- ✔ Noticeable drop in fuel economy for no apparent reason.
- ✔ Rough or erratic idling and stalling.
- ✔ The transmission shifts harshly or at the wrong times.
- ✔ Failure to pass an emissions or smog test.
- ✔ Seemingly unrelated warning lights appearing on the dashboard.
A Straightforward Guide to Installation
Replacing the 2009-2011 Lucerne ECM is a job most DIYers can handle. On the Lucerne, it’s conveniently located in the lower part of the air cleaner box assembly. Always consult a repair manual for your specific vehicle, but here are the general steps:
- Safety First: Disconnect the negative terminal from your vehicle’s battery and wait at least 15 minutes for the system capacitors to discharge.
- Locate the ECM: On the 4.6L Lucerne, you’ll need to access the air cleaner box. The ECM is typically mounted to the lower portion of this housing.
- Disconnect Connectors: Carefully release the locking tabs on the main electrical wiring harnesses and gently pull them straight out from the module. Never force them.
- Remove the Old Module: Unbolt the old ECM from its mounting bracket. Pay attention to any grounding straps and ensure they are clean and secure.
- Install the New Module: Mount your new, pre-programmed ECM in place. Reconnect the wiring harnesses, making sure they click securely into place.
- Reconnect Battery: Reattach the negative battery terminal.
- Perform Security Relearn: You will likely need to perform a simple security relearn procedure. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times before starting the engine. This allows the new ECM to sync with your vehicle’s anti-theft system.
Verified Vehicle Compatibility List
This module is a direct replacement for a wide array of GM vehicles and is interchangeable with part numbers 12639300, 1263605, 12628993, 12628911, 12625453, 12622175, 12630464, and 12678512. Please confirm your vehicle is on this list:
- ✔ Buick Lucerne: 2009-2011 (4.6L, located in lower air cleaner box)
- ✔ Cadillac CTS: 2009 (6.2L)
- ✔ Cadillac DTS: 2009-2011
- ✔ Cadillac SRX: 2009 (4.6L)
- ✔ Cadillac STS: 2009 (4.4L, 4.6L), 2010 (4.6L)
- ✔ Cadillac XLR: 2009 (ID 12636659 or 12625453)
- ✔ Chevrolet Colorado: 2009-2012 (2.9L, 3.7L)
- ✔ Chevrolet Corvette: 2009 (ZR1)
- ✔ Chevrolet Trailblazer: 2009 (6.0L)
- ✔ GMC Canyon: 2009-2012 (2.9L, 3.7L)
- ✔ GMC Envoy: 2009 (5.3L)
- ✔ Hummer H3: 2009-2010 (3.7L)
- ✔ Saab 9-7X: 2009
Frequently Asked Questions
Do I need to do any programming myself?
No. We handle all the programming before we ship the part. We use your VIN to load the correct, updated GM software, making it ready for installation right out of the box.
Why do you need my VIN?
Your Vehicle Identification Number (VIN) is essential. It allows us to access the exact software calibration file for your car’s specific options, engine, and transmission. This ensures perfect compatibility and performance.
Is this a simple plug-and-play installation?
Almost. After physically installing the module, you will need to perform a simple ‘Security Relearn Procedure’ which syncs the new ECM to your car’s anti-theft system. This procedure requires no special tools and instructions are readily available online or in our guide above.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the ECM (common codes P0601-P0606) or a related communication error, then yes, this will resolve the issue. It’s crucial to properly diagnose the root cause before ordering.
Are there any core charges or fees?
No, there is no core charge for this part. You do not need to send your old, faulty module back to us.