If you’re dealing with the frustration of a transmission that won’t shift correctly, goes into limp mode, or throws a check engine light, you’ve come to the right place. As a technician with over two decades of experience under the hood, I’ve seen firsthand how a failing Transmission Control Module (TCM) can sideline an otherwise perfectly good vehicle. This isn’t just a part; it’s the solution to get your 2006 Envoy XL TCM system operating like new again, restoring the smooth, predictable performance you depend on.
This is a direct-fit T42 Transmission Control Module, part number 24243921, for a wide range of General Motors vehicles. The most critical feature? It arrives at your door fully programmed to your vehicle’s specific VIN. This means you can skip the expensive and time-consuming trip to the dealership for programming. It’s a true plug-and-play fix designed for both professional installers and determined DIYers.
From the Diagnostic Bay: The Silverado That Wouldn’t Shift
A customer brought in his 2008 Silverado 1500, complaining of harsh 1-2 shifts and occasionally getting stuck in 3rd gear (limp mode). He had already spent a few hundred dollars replacing shift solenoids based on a forum recommendation, but the problem persisted. His scanner showed a generic P0700 (Transmission Control System Malfunction) code. After a quick diagnostic, I confirmed the solenoids were fine. The real culprit was a faulty TCM creating intermittent communication drops. We installed one of our VIN-programmed T42 modules. In less than 20 minutes, the truck was shifting perfectly, and the codes were gone for good. This case is a classic example: replacing the brain, not just the symptoms, is often the key to a lasting repair.
Is Your GM Vehicle Exhibiting These Transmission Faults?
A failing TCM can manifest in numerous ways. If you’re experiencing any of the following, this module is the likely solution:
- ✔ Harsh, slamming, or erratic gear shifts.
- ✔ Delayed engagement when shifting from Park to Drive or Reverse.
- ✔ Vehicle is stuck in one gear (often called “limp mode”).
- ✔ Check Engine Light or Transmission Warning Light is illuminated.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750, P0753, P0758, or other solenoid-related faults.
- ✔ Poor fuel economy and a feeling of lost power.
- ✔ The torque converter fails to lock up at highway speeds.
A Straightforward Guide to TCM Installation
One of the best parts about this module is its simple installation. You don’t need a vehicle lift or specialized tools. For most models, including the 2006 Envoy XL TCM replacement, the process takes under 30 minutes.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and help reset the system.
- Locate the Module: The TCM is typically found in the engine bay. Common locations include the LH (driver’s side) engine compartment, next to the battery, or under the air cleaner box. Check your specific model’s location from the list below.
- Disconnect and Remove: Carefully unplug the electrical connectors. They have locking tabs, so be gentle. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, VIN-programmed TCM into place and securely reconnect the electrical harnesses. You should hear a click as they lock.
- Final Steps: Reconnect the battery terminal. Start the vehicle and use a standard OBD2 scan tool to clear any stored fault codes. Take the vehicle for a test drive to confirm smooth shifting.
Verified Vehicle Compatibility List
This module is a direct replacement for part number 24243921 and other interchangeable numbers on the following GM models. Please verify your vehicle’s specific location noted in parentheses.
- ENVOY XL (2006): Transmission; (LH engine compartment), (8 cylinder)
- Chevrolet Avalanche 1500 (2007-2008): Transmission; (next to battery)
- Chevrolet Cobalt (2006-2010): Transmission; (LH strut tower)
- Chevrolet Express/GMC Savana 1500/2500/3500 (2006-2014): Transmission; (RH engine compartment)
- Chevrolet HHR (2006-2011): Transmission; (LH engine compartment)
- Chevrolet Impala (2006-2011): Transmission; (lower air cleaner housing)
- Chevrolet Silverado/GMC Sierra 1500 (2007-2013): Transmission; (next to battery)
- Chevrolet Tahoe/GMC Yukon (2007-2009): Transmission; (next to battery)
- Buick Allure/LaCrosse (2006-2009): Transmission; (lower air cleaner housing)
- Cadillac DTS (2006-2011): Transmission; (RH front engine compartment)
- GMC Envoy (2006-2009): Transmission; (LH engine compartment)
- Pontiac G6 (2006-2010): Transmission; (LH strut tower)
- Saturn Aura (2007-2009): Transmission; (LH frame rail front)
- And many more models listed in the original fitment data.