Restore Peak Performance to Your GM Truck’s Transmission
If your 2007 GMC Sierra 2500 is suffering from erratic shifting, getting stuck in gear, or throwing transmission-related check engine light codes, a failing Transmission Control Module (TCM) is the most likely culprit. As a seasoned technician, I’ve seen countless GM trucks come into the shop with these exact issues. The T42 TCM is the electronic brain of your 4-speed automatic transmission (like the 4L80E in your Sierra), and when it fails, it can make your powerful truck feel unreliable and unsafe. This replacement T42 TCM, part number 24243921, is the definitive solution to get your truck operating smoothly and dependably again.
We take the guesswork and extra cost out of the repair. Unlike a generic module from a parts store, this unit comes expertly pre-programmed to your truck’s specific Vehicle Identification Number (VIN). This means no expensive trips to the dealership for programming—it’s a true plug-and-play fix. By installing this module, you are directly addressing the root cause of many common transmission problems, ensuring your gear changes are crisp, your torque converter locks up correctly, and your fuel efficiency returns to normal. This is the same reliable fix I’d perform in my own service bay for a 2007 Sierra 2500 TCM failure.
Case Study: The Limp Mode Sierra 2500
A contractor brought his ’07 Sierra 2500 HD into my shop, completely frustrated. His truck was stuck in what we call ‘limp mode’—it wouldn’t shift past 3rd gear. He was losing time and money. His scanner showed a P0700 (Transmission Control System Malfunction) and a few solenoid circuit codes. Instead of starting a costly transmission teardown, we checked the basics. The fluid was fine, and the wiring harness looked good. The culprit was the original TCM, which was failing intermittently. We installed one of our VIN-programmed modules. The entire job took less than 30 minutes, and after clearing the codes, the truck shifted perfectly on the test drive. He was back on the job site the same afternoon, saving hundreds compared to a dealership visit.
Is Your Sierra 2500 Exhibiting These Transmission Problems?
- ✔ Harsh, banging shifts or delayed gear engagement.
- ✔ Vehicle is stuck in a single gear (limp mode) and won’t shift up or down.
- ✔ The Check Engine Light or Transmission Warning Light is on.
- ✔ Diagnostic Trouble Codes (DTCs) like P0700, P0751, P0756, or other solenoid-related faults are present.
- ✔ Sudden loss of power or poor acceleration due to incorrect gear selection.
- ✔ A noticeable drop in fuel economy.
A Straightforward Guide to Installation
Replacing the 2007 Sierra 2500 TCM is a simple job that most DIYers can handle in their own driveway. For this specific truck, it’s conveniently located right next to the battery in the engine compartment.
- Safety First: Always disconnect the negative terminal from your truck’s battery before starting any electronic work.
- Locate the Module: Open the hood and find the TCM mounted next to the battery tray on the driver’s side.
- Disconnect and Remove: Carefully unplug the large electrical connectors. Be gentle with the locking tabs. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, VIN-programmed TCM into place. Securely reconnect the electrical connectors until they click.
- Final Steps: Reconnect the battery terminal. While the module is plug-and-play, it’s best practice to use a basic OBD2 scan tool to clear any stored fault codes from the vehicle’s memory. Start the truck and enjoy smooth shifting!
Verified Fitment For Your General Motors Vehicle
This T42 TCM is a direct replacement for part number 24243921 and other service numbers listed below. It fits a wide range of GM cars and trucks from 2006-2014 equipped with 4-speed automatic transmissions. While this page is focused on the 2007 Sierra 2500 TCM, please confirm your model in the list below for guaranteed compatibility.
This part will fit these makes and models with these options
SIERRA 2500 PICKUP 07 Transmission; new style (smooth door skin), 6.0L, (next to battery)
SILVERADO 2500 PICKUP 07 Transmission; new style (smooth door skin), 6.0L, (next to battery)
… and many more GM vehicles including Tahoe, Suburban, Express, Savana, Yukon, etc.
Frequently Asked Questions
Do I need to get this module programmed by a dealer?
No. This module arrives pre-programmed to your vehicle’s VIN. You just need to provide your VIN at checkout. This saves you the time and expense of a dealership visit, making it a true plug-and-play installation.
What is the main function of the TCM?
The Transmission Control Module (TCM) acts as the computer for your automatic transmission. It receives data from various sensors on the engine and vehicle to control shift points, line pressure, and torque converter lockup for optimal performance and fuel efficiency.
Will this fix a P0700 check engine light code?
A P0700 code is a general fault code indicating the TCM has detected a problem. While this module often resolves the underlying issue causing the P0700 (like internal circuit failure), you should always diagnose any other specific codes (e.g., for solenoids or sensors) that are present alongside it.
Is there a core charge for my old part?
No, there is no core charge required for this part. You can keep or dispose of your old module without the hassle of returning it.
Where is the TCM located on my 2007 Sierra 2500?
On the 2007 GMC Sierra 2500 (new body style), the TCM is located in the engine compartment, mounted on a bracket right next to the battery.