Get Your GMC Envoy Shifting Smoothly Again
Is your 2006-2009 GMC Envoy driving you crazy with unpredictable shifting, getting stuck in gear, or flashing a check engine light? You’re not alone. The Transmission Control Module (TCM), the electronic brain of your automatic transmission, is a common failure point. When it fails, it can make your reliable SUV feel unsafe and unpredictable. Instead of facing a massive bill and a long wait at the dealership, take control of the repair with our pre-programmed T42 Transmission Control Module, part number 24234503.
As a technician with over two decades of experience, I’ve seen countless GM vehicles sidelined by faulty electronics. A failing TCM isn’t just an annoyance; it can lead to poor fuel economy, excessive heat, and even permanent damage to your transmission’s mechanical parts. This module is a direct-fit, OEM-quality solution designed to restore the precise, factory-new performance your vehicle once had. We handle the complicated part—the VIN programming—so you can enjoy a simple, plug-and-play installation.
Case Study: A Tricky Diagnosis
A customer brought in a 2008 Envoy that was stuck in what he called “get-home mode.” It wouldn’t shift past 3rd gear, and the shifts were harsh and jarring. He’d already replaced two shift solenoids based on a generic code reader’s output, with no improvement. After plugging in my professional scan tool, I saw the tell-tale P0700 (Transmission Control System Malfunction) code, but more importantly, I noticed intermittent communication loss with the TCM itself. This is a classic sign that the module’s internal processor is failing, not the solenoids it controls. We installed one of our VIN-programmed TCMs, and in under an hour, the Envoy was shifting perfectly. The customer saved hundreds by avoiding unnecessary parts and dealer programming fees.
Is Your GMC Envoy Showing These Warning Signs?
- ✔ Harsh, slamming shifts or delayed gear engagement.
- ✔ Vehicle is stuck in “limp mode” (usually 2nd or 3rd gear) and won’t shift up or down.
- ✔ The check engine light or transmission warning light is on with codes like P0700, P0750, or other solenoid-related DTCs.
- ✔ A noticeable drop in fuel efficiency.
- ✔ The transmission feels like it’s slipping between gears.
- ✔ Complete loss of communication with the TCM, preventing diagnostics.
A Straightforward Guide to Your 2006-2009 Envoy TCM Installation
This is a repair you can confidently tackle in your own driveway. For the GMC Envoy, the TCM is conveniently located in the engine compartment on the driver’s side (LH). No specialized tools are required.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the system.
- Locate the Module: Open the hood and find the TCM on the left-hand (driver’s) side of the engine compartment. It’s a silver box with several electrical connectors.
- Disconnect and Remove: Carefully unplug the electrical harnesses. They have locking tabs that need to be depressed. Once disconnected, unbolt the old module from its mounting bracket.
- Install the New TCM: Bolt the new, VIN-programmed module into place. Securely plug in the electrical connectors until they click, ensuring a solid connection.
- Final Steps: Reconnect the battery terminal. Start the vehicle and let it run for a few moments. While our programming resolves most codes, it’s good practice to use a basic OBD2 scanner to clear any stored fault codes to ensure a clean slate.
Verified Vehicle Compatibility
This T42 TCM is a direct replacement for part number 24234503 and is interchangeable with many other service numbers. It fits a wide range of General Motors vehicles. While this page focuses on the Envoy, please verify your specific model in the list below.
- GMC Envoy / Envoy XL / Trailblazer / Trailblazer EXT (2006-2009): Found in the LH engine compartment.
- Chevrolet Silverado / GMC Sierra 1500, 2500 (2007-2013): Typically located next to the battery.
- Chevrolet Tahoe / Suburban / GMC Yukon (2007-2009): Found next to the battery.
- Chevrolet Express / GMC Savana Vans (2006-2014): Located in the RH engine compartment.
- Buick LaCrosse / Allure / Lucerne (2006-2011): Found under the air cleaner housing or in the LH engine compartment.
- Cadillac DTS (2006-2011): Located in the RH front engine compartment.
- Pontiac G6 / Grand Prix (2006-2010): Found on the LH strut tower.
- And many more models including the HHR, Cobalt, Saturn Vue, Saab 9-7X, and Hummer H3.
Why is VIN programming so important?
Why is VIN programming so important?
VIN programming loads your vehicle’s specific software and calibrations onto the module. This ensures the TCM communicates perfectly with your engine, ABS, and other systems, controlling shift points and pressures exactly as the factory intended. Skipping this step is why a generic module from a parts store won’t work correctly. We do it for you, so it’s ready to install right out of the box.
Is this a difficult part to install for a DIYer?
Not at all. This is one of the more accessible electronic repairs. On most compatible vehicles, including the 2006-2009 Envoy, the TCM is easy to access in the engine bay. With basic hand tools and our guide, most people can complete the swap in under 30 minutes.
Do I need to send my old part back? Is there a core charge?
No. We do not require a core return for this part. You can keep or dispose of your old module without any additional hassle or charges.
Will this part fix my check engine light?
If your check engine light is on due to a faulty TCM throwing codes like P0700 or other transmission-related faults, then yes, this part is the correct solution. It’s designed to resolve these specific electronic failures.