If your 2006-2009 GMC Envoy is suffering from erratic shifting, getting stuck in gear, or has the check engine light on with transmission codes, you’ve come to the right place. As a technician with over two decades of experience, I’ve seen firsthand how a faulty Transmission Control Module (TCM) can bring an otherwise solid vehicle to a standstill. The TCM is the brain of your automatic transmission, and when it fails, it can cause a cascade of frustrating and concerning problems. This isn’t just an inconvenience; it’s a critical failure that impacts your vehicle’s drivability and safety.
This T42 Transmission Control Module is the definitive solution for these issues. It arrives at your door fully pre-programmed to your Envoy’s specific Vehicle Identification Number (VIN). This means you can skip the expensive and time-consuming trip to the dealership for programming. It’s a direct, plug-and-play fix designed to restore the crisp, predictable shifting you expect from your truck. By replacing your old unit, you’re not just fixing a symptom—you’re addressing the root cause of common transmission woes and preventing further damage to sensitive internal components.
Case Study: A Tricky Diagnosis
I remember a 2008 Envoy that came into the shop with a very intermittent issue. The owner said it would randomly refuse to shift out of 2nd gear, but only after driving for 20-30 minutes. No consistent codes, just a general P0700 (Transmission Control System Malfunction) every now and then. We checked the fluid, wiring, and solenoids—all looked fine. Experience pointed to the TCM. Heat soak was causing an internal failure in the module. We installed a VIN-programmed 2006-2009 Envoy TCM, and the problem vanished instantly. The customer was thrilled to have a reliable vehicle back without the guesswork of a costly transmission teardown.
Is Your Envoy Exhibiting These Telltale Signs?
- ✔ Harsh, slamming shifts or delayed gear engagement.
- ✔ Vehicle is stuck in a single gear (often called “limp mode”).
- ✔ The check engine light or transmission warning light is illuminated.
- ✔ Diagnostic Trouble Codes (DTCs) like P0700, P0750, or other solenoid-related faults are present.
- ✔ A sudden drop in fuel economy or a transmission that seems to be overheating.
- ✔ Complete loss of communication with the transmission module.
A Straightforward 30-Minute Installation Guide
Replacing the TCM on your Envoy is a job most DIYers can handle with basic tools. For the 2006-2009 GMC Envoy, the module is typically found in the left-hand (driver’s side) engine compartment.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- Locate the TCM: Find the module in the driver’s side engine bay. It will have several large electrical connectors attached.
- Disconnect and Remove: Carefully unplug the electrical harnesses. Then, unbolt the module from its mounting bracket and remove it from the vehicle.
- Install the New Module: Mount your new, pre-programmed TCM in the same location and securely fasten it. Reconnect the electrical harnesses, ensuring they click into place.
- Final Steps: Reconnect the battery terminal. While the module is plug-and-play, it’s good practice to use a scan tool to clear any stored DTCs from the system’s memory.
Verified Vehicle Compatibility
This T42 TCM, equivalent to part number 24252114, is engineered for a precise fit in your 2006-2009 Envoy TCM application. It is also compatible with a wide range of other GM vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. Key compatible models include:
- GMC Envoy / Envoy XL / Trailblazer / Trailblazer EXT (8 cylinder models)
- Chevrolet Silverado & GMC Sierra 1500
- Chevrolet Tahoe & GMC Yukon
- Chevrolet Impala & Monte Carlo
- Buick LaCrosse & Lucerne
- Pontiac G6 & Grand Prix
- Hummer H3 & Saab 9-7X
- And many more GM cars, trucks, and vans from 2006-2014.
Frequently Asked Questions
Frequently Asked Questions
What is the main benefit of a VIN-programmed TCM?
A VIN-programmed module is ready for installation right out of the box. It has the correct software and calibrations for your specific vehicle, eliminating the need for expensive dealership programming and ensuring optimal transmission performance.
Do I need to visit a mechanic after installing this part?
No. Because this module is pre-programmed to your VIN, it is a plug-and-play solution. No further programming or professional setup is required, saving you time and money.
Is this a difficult part to install myself?
For most individuals with basic mechanical skills, this is a very manageable job. The module is easily accessible in the engine bay, and the replacement typically takes less than 30 minutes.
What could happen if I ignore a failing TCM?
Continuing to drive with a faulty TCM can lead to poor fuel mileage, unpredictable shifting, and potentially severe damage to your transmission’s mechanical parts due to incorrect fluid pressures and shift commands.
Is there a core charge for my old part?
No, there is no core charge. You can keep your old part without any extra hassle or fees.