If your 2006-2009 Buick LaCrosse is suffering from harsh shifting, getting stuck in gear, or has an illuminated check engine light, you’re likely dealing with a failed Transmission Control Module (TCM). As an experienced technician, I’ve seen these symptoms countless times. Drivers come into the shop frustrated with their car’s unpredictable behavior, worried about a massive transmission repair bill. The good news is that the fix is often simpler and more affordable than you think.
This T42 Transmission Control Module, corresponding to part number 24235340, is the definitive solution to restore your vehicle’s transmission performance. The TCM is the brain of your automatic transmission, responsible for managing shift points, controlling torque converter lockup, and monitoring system health. When it fails, the communication breaks down, leading to the problems you’re experiencing. Our module is a direct-fit replacement, built to meet or exceed original equipment standards for reliability and longevity.
A Technician’s Notebook
I recall a 2008 Buick LaCrosse that came into my bay with a persistent P0700 (Transmission Control System Malfunction) code and a complaint of ‘slamming’ into gear. The owner had already replaced a shift solenoid with no improvement. After hooking up my scan tool, I could see the TCM was sending erratic commands and occasionally losing communication altogether. Heat and vibration, especially given its location under the air cleaner box, had taken their toll on the internal circuits. We installed one of our VIN-programmed T42 modules, and the difference was immediate. The shifts were smooth, the code was gone, and the customer was relieved to have their car back without needing a full transmission rebuild.
Is Your LaCrosse Exhibiting These Transmission Problems?
A failing TCM can manifest in several ways. If you notice any of the following, it’s a strong indicator that your module needs replacement. A proper diagnosis with a scan tool is always recommended, but these are the classic signs:
- ✔ Harsh, delayed, or erratic gear shifts.
- ✔ Vehicle is stuck in one gear (often called ‘limp mode’).
- ✔ Check Engine Light or Transmission Warning Light is on.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750, or other solenoid-specific codes.
- ✔ Poor acceleration and decreased fuel economy.
- ✔ The transmission feels like it’s slipping between gears.
- ✔ Complete loss of shifting capability.
Your Straightforward 30-Minute Installation Guide
One of the best features of this module is that it comes pre-programmed to your vehicle’s VIN. This eliminates the need for expensive dealership programming, making it a perfect job for a DIY enthusiast or any professional mechanic. For the 2006-2009 Buick LaCrosse, the process is very accessible.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the system.
- Locate the TCM: On your LaCrosse, the TCM is conveniently located under the lower air cleaner housing in the engine compartment. You will need to remove the air cleaner assembly to access it.
- Disconnect and Remove: Carefully unplug the electrical connectors from the old TCM. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new TCM into place and securely reconnect the electrical harnesses. Ensure they click into place.
- Reassemble and Reconnect: Reinstall the air cleaner housing. Once everything is back in place, reconnect the negative battery terminal.
- Final Steps: Start the vehicle. It’s a good practice to use a basic OBD2 scan tool to clear any stored fault codes from the engine computer (ECM). Take the vehicle for a test drive to confirm the shifting issues are resolved.
Why Choose Our Programmed 2006-2009 LaCrosse TCM?
This isn’t just a replacement part; it’s a complete solution. By programming the module with the latest GM software updates tied to your specific VIN, we ensure flawless communication between the TCM, the engine computer, and the transmission itself. This results in optimized shift strategies, improved fuel efficiency, and a longer life for your transmission. This module is also interchangeable with a wide range of part numbers, including 24252114, 24234503, and 24240449, making it a versatile fix for many GM vehicles.
Verified Fitment for Your General Motors Vehicle
This T42 Transmission Control Module is a confirmed fit for the following vehicle:
- Buick LaCrosse (2006, 2007, 2008, 2009) – Located under the lower air cleaner housing.
It is also compatible with a wide array of other GM models such as the Chevrolet Impala, GMC Sierra, Cadillac DTS, Pontiac G6, and more. Please verify the part number or use our vehicle selector to ensure perfect compatibility.
Frequently Asked Questions
Is this part really plug-and-play?
Yes. We program the module to your vehicle’s specific VIN before shipping. This means it arrives ready for installation without any need for a trip to the dealership for additional programming.
Where is the TCM on my 2007 LaCrosse?
On the 2006-2009 Buick LaCrosse, the Transmission Control Module is located in the engine bay, underneath the air cleaner box assembly.
Do I need to return my old part?
No, there is no core charge for this part. You can keep your old module, which saves you the time and hassle of a return shipment.
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 (like internal failure), it’s important to ensure there are no other issues, such as faulty wiring or solenoids. However, a defective TCM is a very common cause for this code.
What happens if I don’t replace a bad TCM?
Continuing to drive with a faulty TCM can lead to progressively worse shifting, poor fuel mileage, and can eventually cause excessive wear and permanent mechanical damage to your transmission, leading to a much more expensive repair.