If your 2007 GMC Sierra 2500 is suffering from harsh shifting, getting stuck in gear, or throwing transmission codes, you’re not just dealing with an annoyance—you’re facing a critical failure that can sideline your workhorse truck. As a technician with over two decades of experience, I’ve seen countless GM trucks come into the shop with these exact issues. The culprit is almost always a faulty Transmission Control Module (TCM). This VIN-programmed T42 TCM is the definitive, dealership-free solution to restore your truck’s transmission performance and get you back on the road with confidence.
This isn’t just a replacement part; it’s a direct fix for the electronic brain of your 4L80E or other compatible GM automatic transmission. It precisely manages shift points, torque converter lockup, and line pressure. When it fails, the symptoms can be dramatic and often misdiagnosed as internal transmission damage. By replacing your old unit with this pre-programmed module, you are installing a component loaded with the latest GM software specific to your truck’s VIN, ensuring seamless communication and optimal function right out of the box. This eliminates the need for expensive dealership programming or specialized tools, making it a perfect repair for both professional mechanics and capable DIYers.
From the Diagnostic Bay: A Sierra’s Shifting Nightmare
A customer brought in his ’07 Sierra 2500 HD, a work truck that was his livelihood. The complaint was severe: it would slam into gear from a stop and sometimes refuse to shift past 3rd gear (limp mode), flashing a P0700 code. He was worried he needed a full transmission rebuild, a multi-thousand-dollar job. After connecting my scan tool, I saw several solenoid circuit codes alongside the P0700. While this can point to solenoids, my experience with these T42 modules told me to check the source. We swapped in a VIN-programmed TCM, cleared the codes, and took it for a test drive. The shifting was immediately smooth and predictable. The module itself had failed internally, sending erratic signals. This simple swap saved the customer thousands of dollars and days of downtime. That’s the power of a correct diagnosis and a quality part.
Is Your Sierra Exhibiting These Transmission Faults?
A failing TCM can manifest in several ways. If you’re experiencing any of the following, it’s highly likely your 2007 Sierra 2500 Transmission Control Module is the root cause:
- ✔️ Harsh, delayed, or erratic gear changes.
- ✔️ Vehicle is stuck in “limp mode” (usually 2nd or 3rd gear).
- ✔️ Check Engine Light or Transmission Warning Light is on.
- ✔️ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750-P0758, or other solenoid-related faults.
- ✔️ The transmission refuses to upshift or downshift properly.
- ✔️ A noticeable decrease in fuel economy.
- ✔️ Intermittent loss of communication with the TCM.
A Straightforward Guide to Installation
Installing your new TCM is a simple process that can be done in your driveway in under 30 minutes with basic hand tools. For the 2007 Sierra 2500, the module is conveniently located right next to the battery in the engine compartment.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts and to help reset the system.
- Locate the TCM: Open the hood and find the TCM mounted next to the battery. It’s a silver box with several large electrical connectors.
- Disconnect and Remove: Carefully unplug the electrical connectors. They have locking tabs that may need to be gently pried. Once disconnected, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, VIN-programmed TCM into place. Securely reconnect the electrical harnesses, ensuring they click into place.
- Final Steps: Reconnect the negative battery terminal. Start the vehicle and allow it to idle for a few minutes. If you have a basic scan tool, it’s good practice to clear any stored fault codes from the ECU.
Verified Vehicle Compatibility
This module is a direct-fit replacement for a wide range of General Motors vehicles equipped with the T42 TCM. While this page is focused on the 2007 Sierra 2500 Transmission Control Module, it is also compatible with the following models. Always verify your part number (24238856) or contact us with your VIN for guaranteed fitment.
- GMC: Sierra 1500/2500, Yukon, Yukon XL, Savana, Envoy, Canyon
- Chevrolet: Silverado 1500/2500, Tahoe, Suburban, Avalanche, Express, Colorado, Impala, Cobalt, HHR
- Cadillac: DTS
- Buick: LaCrosse, Lucerne, Rainier
- Pontiac: G6, Grand Prix
- And more, including select Hummer, Saab, and Saturn models.
Frequently Asked Questions
Do I need to have this TCM programmed by a dealer?
No. This is the biggest benefit of our service. We pre-program the module to your vehicle’s specific VIN before shipping. It arrives ready for plug-and-play installation, with no extra programming or dealer visits required.
Is a core charge required?
No, we do not require a core charge. You can keep your old part, so there’s no hassle with return shipping or waiting for a refund.
Will this fix a P0700 trouble code?
A P0700 code is a general transmission fault request from the TCM to the ECM to turn on the check engine light. In many cases where the TCM itself has failed, replacing it with this programmed unit will resolve the P0700 and any accompanying specific transmission codes.
What is the warranty on this part?
This transmission control module comes with a one-year warranty, giving you peace of mind and assurance in the quality and reliability of your repair.
Where is the TCM located on my 2007 Sierra 2500?
On the 2007 Sierra 2500 (new body style), the transmission control module is located in the engine compartment, mounted on a bracket right next to the battery.