Restore Smooth Shifting to Your Buick LaCrosse
If your 2006-2009 Buick LaCrosse is suffering from harsh shifting, delayed gear engagement, or has thrown a transmission-related check engine light, you’re likely dealing with a failing Transmission Control Module (TCM). As an experienced technician, I’ve seen countless GM vehicles, including the LaCrosse, come into the shop with these exact issues. The T42 TCM is the brain of your automatic transmission, and when it fails, it can make your daily drive frustrating and unreliable. This replacement TCM, part number 24243921, is the definitive solution to get your car’s transmission performing like new again.
We take the guesswork and high dealership costs out of the equation. Each module is expertly programmed to your vehicle’s specific VIN before it ships. This means no expensive trips to the dealer for programming—it arrives ready for a true plug-and-play installation. This is a critical step that ensures all the learned shift adaptations and vehicle-specific settings are correct from the moment you turn the key, resolving common diagnostic trouble codes (DTCs) and restoring factory performance.
Diagnosing a Faulty 2006-2009 LaCrosse Transmission Control Module
A failing TCM can manifest in several ways, often starting as intermittent problems that worsen over time. The constant heat cycles and vibrations in the engine bay take their toll on the delicate electronics inside. If you’re experiencing any of the symptoms below, a faulty TCM is the most probable cause. Replacing it with a quality, pre-programmed part is the most effective way to address the root of the problem and prevent further damage to your transmission’s mechanical components.
A Technician’s Notebook: The Intermittent Shifting Ghost
I had a 2008 Buick LaCrosse in my bay that was a real head-scratcher for the owner. He said it would randomly slam into gear, but only after it was fully warmed up. Other times, it drove perfectly. He’d already replaced a shift solenoid with no luck. When I hooked up my scan tool, I saw a history code for P0700 (Transmission Control System Malfunction) but nothing active. After letting the car idle for 30 minutes to replicate the heat soak condition, the harsh shifts returned, along with a P0752 (Shift Solenoid ‘A’ Stuck On) code. The solenoids tested fine, which pointed directly to the TCM itself providing faulty commands. A new, VIN-programmed TCM fixed it instantly. It’s a classic failure pattern for these modules.
Common Signs of a Failing T42 TCM
- ✔ Harsh, erratic, or delayed gear shifts.
- ✔ Vehicle gets stuck in “limp mode” (usually 2nd or 3rd gear).
- ✔ Check Engine Light or Transmission Warning Light is on.
- ✔ Diagnostic Trouble Codes (DTCs) like P0700, P0750, P0752, or other solenoid-related faults are present.
- ✔ The transmission refuses to upshift or downshift properly.
- ✔ A noticeable decrease in fuel economy.
- ✔ Complete loss of communication with the TCM.
A Straightforward Guide to Installation
For the Buick LaCrosse, this is a job most DIY enthusiasts can handle in their driveway in under 30 minutes. The TCM is typically located under the lower air cleaner housing, making it easily accessible.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the vehicle’s electronic systems.
- Locate the Module: Find the TCM, which is situated beneath the air cleaner box on your 2006-2009 LaCrosse. You may need to remove the air cleaner assembly to gain access.
- Disconnect and Remove: Carefully unplug the electrical connectors from the old TCM. Press the release tabs firmly to avoid breaking them. Once disconnected, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, pre-programmed TCM into place. Reconnect the electrical harnesses, ensuring they click securely into position.
- Final Steps: Reinstall the air cleaner assembly and reconnect the battery terminal. While our programming handles the critical setup, it’s good practice to use a basic scan tool to clear any stored fault codes from other modules.
Will This Fit My Vehicle?
This T42 Transmission Control Module is a direct-fit replacement for the 2006-2009 Buick LaCrosse. It is also compatible with a wide range of other GM vehicles that use the same T42 controller. Please verify your part number or contact us with your VIN to ensure perfect compatibility. This part interchanges with service numbers such as 24243921, 24234503, 24252114, and more.
Frequently Asked Questions
Do I need to have this module programmed by a dealer?
No. We pre-program the module to your vehicle’s VIN before shipping. It arrives ready for installation, saving you time and money on dealership programming fees.
Is there a core charge for my old part?
No, there is no core charge. You can keep your old part without any hassle or need to return it.
Will this fix a P0700 trouble code?
A P0700 code is a general fault request from the TCM to the Engine Control Module (ECM) to turn on the Check Engine Light. While this module often resolves the underlying issue causing the P0700, you should scan for more specific transmission codes (like P07xx) to confirm the diagnosis.
What tools are needed for installation on a LaCrosse?
Installation typically requires only basic hand tools, such as a socket set and ratchet to remove the air cleaner housing and unbolt the module. No specialized equipment is necessary.
What kind of warranty is included?
This part comes with a one-year warranty, giving you peace of mind and assurance in the quality and reliability of your repair.