Is Your Buick LaCrosse Shifting Erratically?
If you’re experiencing harsh shifting, delayed gear engagement, or a check engine light on your 2006 to 2009 Buick LaCrosse, a failing Transmission Control Module (TCM) is the most likely culprit. The TCM is the electronic brain of your automatic transmission, responsible for orchestrating every gear change, managing torque converter lockup, and ensuring smooth, efficient operation. When it begins to fail, it can cause a wide range of frustrating and potentially damaging issues, from poor fuel economy to being stuck in ‘limp mode’. Don’t let a faulty module sideline your vehicle. This direct-fit, VIN-programmed T42 TCM is the definitive solution to restore your transmission’s performance and reliability.
From the Diagnostic Bay
We had a 2008 Buick LaCrosse come into the shop with the classic symptoms: banging into gear and a P0700 trouble code. The owner had already replaced two shift solenoids based on a generic code reader’s suggestion, but the problem persisted. After a quick scan with professional equipment, we confirmed the issue wasn’t the solenoids themselves, but the TCM’s inability to properly command them. The internal drivers had failed. We installed a VIN-programmed T42 module, cleared the codes, and the car shifted like it just rolled off the assembly line. This highlights why it’s crucial to address the root cause—the TCM—rather than just chasing symptoms.
Why Choose Our Programmed 2006-2009 LaCrosse TCM?
This isn’t just a replacement part; it’s a complete, ready-to-install solution. The biggest hurdle in replacing a modern TCM is the need for expensive and time-consuming dealership programming. We eliminate that step entirely. By providing us with your vehicle’s VIN during checkout, we program the module with the latest GM software specific to your LaCrosse. This ensures perfect communication between the engine, transmission, and other vehicle systems right out of the box. It’s a true plug-and-play repair that saves you time, money, and a trip to the dealer.
Common Symptoms of a Failing LaCrosse TCM
- ✔ Erratic Shifting: Experiencing harsh, jerky, or delayed shifts between gears.
- ✔ Warning Lights: The Check Engine Light or a dedicated transmission warning light is illuminated on your dashboard.
- ✔ Diagnostic Trouble Codes (DTCs): Common codes include P0700 (Transmission Control System Malfunction), P0750-P0758 (Shift Solenoid errors), or other transmission-related faults.
- ✔ Stuck in Gear: The vehicle may enter a fail-safe or ‘limp mode’, often getting stuck in 2nd or 3rd gear.
- ✔ No Upshift/Downshift: The transmission refuses to shift into higher or lower gears as needed.
- ✔ Poor Fuel Economy: Inefficient shifting and torque converter operation can lead to a noticeable drop in MPG.
- ✔ Communication Loss: A scan tool may be unable to communicate with the TCM, indicating a complete module failure.
Guaranteed Fitment and Performance
This genuine OEM-quality T42 TCM, service part number 24243921, is engineered to meet or exceed original factory specifications. It is a direct replacement for a wide range of GM vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. While this page is focused on the 2006-2009 LaCrosse TCM, this module also fits dozens of other models, including the Chevrolet Impala, GMC Sierra, Cadillac DTS, and Pontiac Grand Prix. Its broad compatibility and proven reliability make it the trusted choice for professional technicians and DIY mechanics alike. Every module is backed by our one-year warranty for your peace of mind.
Installation Guide
Installation is straightforward. On the 2006-2009 Buick LaCrosse, the TCM is typically located inside or below the lower air cleaner housing in the engine bay. The process generally takes less than 30 minutes.
- Disconnect the Battery: Always disconnect the negative battery terminal before beginning any electronic component replacement.
- Locate the TCM: Find the module attached to the lower air cleaner housing.
- Disconnect Connectors: Carefully unclip the electrical wiring harnesses from the old module.
- Remove Old Module: Unbolt the old TCM from its mounting point.
- Install New Module: Bolt the new, pre-programmed TCM into place and securely reconnect the wiring harnesses.
- Reconnect Battery: Reattach the negative battery terminal.
- Clear Codes: While not always necessary, it’s good practice to use a scan tool to clear any stored DTCs after installation.
With no core charge, you can keep your old part without the hassle of shipping it back. Get your Buick LaCrosse back on the road and shifting perfectly. Order your pre-programmed TCM today!
Frequently Asked Questions
What does ‘VIN Programmed’ mean?
It means we load the module with your car’s specific Vehicle Identification Number (VIN) and the latest GM software before we ship it. This makes the part plug-and-play, allowing it to communicate correctly with your vehicle’s other computers without requiring a trip to the dealership for expensive programming.
Will this fix a P0700 trouble code?
A P0700 code is a general fault code indicating the TCM has detected a problem. While this module often resolves the root cause of a P0700 and related solenoid codes, you should always perform a full diagnostic. However, if your symptoms align with TCM failure, this part is the correct solution.
Is this part difficult to install myself?
For the 2006-2009 LaCrosse, the installation is relatively simple for someone with basic mechanical skills. It’s located under the air cleaner box and involves disconnecting the battery, unplugging connectors, and swapping the module. The entire process typically takes under 30 minutes.
Do I need to return my old TCM?
No, there is no core charge for this part. You can keep, recycle, or dispose of your old module without any obligation to return it to us.
Is this compatible with other GM vehicles?
Yes, this T42 TCM is compatible with a vast range of GM vehicles from approximately 2006-2014, including many Chevrolet, GMC, Pontiac, Saturn, and Cadillac models. Please verify the part number or use our vehicle fitment tool to ensure compatibility.