End Transmission Headaches in Your Pontiac Grand Prix
If you’re dealing with the frustration of a 2006-2008 Pontiac Grand Prix that shifts harshly, gets stuck in gear, or throws transmission codes, you’ve come to the right place. As a technician with over two decades of experience, I’ve seen countless drivers worry they need a full transmission rebuild when the real culprit is a failed Transmission Control Module (TCM). This T42 TCM, part number 24243921, is the definitive, reliable solution to restore the crisp, predictable performance your car once had.
The TCM is the brain of your automatic transmission. It analyzes data from the engine and speed sensors to command precise gear changes and manage torque converter lockup for optimal fuel economy. When it fails, the result is often erratic behavior that can make your car feel unsafe and unreliable. This module is a direct-fit replacement, but with a key advantage: it comes fully programmed to your vehicle’s specific VIN, eliminating the need for an expensive trip to the dealership for programming.
From the Diagnostic Bay: The Grand Prix That Dodged a Bullet
A customer brought in his ’07 Grand Prix, convinced the transmission was shot. It was slamming into gear and the check engine light was on with a P0700 code. He’d already gotten a quote for over two thousand dollars for a transmission replacement. After a quick scan and check of the basics, I suspected the TCM. These modules, located right under the airbox, are known to fail. We swapped in one of our VIN-programmed units, and in less than an hour, the car was shifting like new. He saved a fortune by correctly diagnosing the electronic failure instead of assuming the worst about the mechanicals.
Is Your Grand Prix Showing These Telltale Signs?
A failing TCM can manifest in several ways. If you’re experiencing any of the following, this module is the likely solution for your 2006-2008 Grand Prix TCM issues:
- ✔ Harsh, banging, or delayed gear shifts.
- ✔ The vehicle is stuck in “limp mode” (usually 2nd or 3rd gear).
- ✔ Check Engine Light or Transmission warning light is illuminated.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700 (Transmission Control System Malfunction) or various solenoid-specific codes (e.g., P0751, P0756).
- ✔ Poor or inconsistent acceleration and decreased fuel efficiency.
- ✔ Complete loss of communication with the TCM, preventing shifting.
DIY Installation: A Straightforward Guide
One of the best features of this part is how simple the installation is, even for a weekend mechanic. No specialized tools are required. For the Pontiac Grand Prix, you’ll find the TCM located under the lower air cleaner housing.
- Safety First: Disconnect the negative terminal from your car’s battery to prevent any electrical shorts and to help reset the system.
- Access the Module: Remove the air cleaner assembly to gain clear access to the old TCM.
- Disconnect and Remove: Carefully unplug the electrical connectors from the module. Then, unbolt the module from its mounting bracket.
- Install the New TCM: Bolt the new, pre-programmed module into place and securely reconnect the electrical harnesses. You’ll hear a click as they lock in.
- Reassemble and Finalize: Reinstall the air cleaner assembly and reconnect the battery terminal. Start the vehicle and allow it to idle for a few minutes. While not always necessary, using a basic OBD2 scanner to clear any stored codes is good practice.
Will This Fit My Vehicle?
This T42 Transmission Control Module is a guaranteed fit for the following vehicles, including serving as a direct replacement for the 2006-2008 Grand Prix TCM. It also interchanges with part numbers 24252114, 24234503, 24230461, and others.
- Pontiac Grand Prix (2006-2008) – Located under the lower air cleaner housing
- Chevrolet Impala (2006-2011)
- Buick LaCrosse / Allure (2006-2009)
- Chevrolet Monte Carlo (2006-2007)
- And many other GM cars, trucks, and SUVs from 2006-2014. Please verify your specific model in our fitment list.
Frequently Asked Questions
What does VIN programming mean?
It means we flash the module with your car’s unique Vehicle Identification Number (VIN) and the latest GM software before we ship it. This ensures it communicates perfectly with your car’s other computers right out of the box, with no dealer programming required.
Do I need to return my old part (core)?
No. There is no core charge for this part. You can keep or dispose of your old module without any hassle or extra fees.
Will this fix a P0700 code?
A P0700 is a generic code indicating the TCM has detected a fault. While this module often resolves the root cause (like an internal short or failed driver circuit), you should ensure the transmission wiring and solenoids are in good condition. In a vast majority of cases I’ve seen, a faulty TCM is the primary cause.
Is this part difficult to install myself?
Not at all. For the Grand Prix, the installation is very accessible and typically takes less than 30-45 minutes with basic hand tools. Our step-by-step guide makes it a simple DIY job.
What if I have questions during installation?
We’re here to help. Our team of experts has hands-on experience with these parts and can provide support to ensure your repair is successful. Your purchase is backed by a one-year warranty for complete peace of mind.