Is your 2006-2009 GMC Envoy suffering from erratic shifting, getting stuck in gear, or throwing transmission-related check engine lights? These are frustrating and often debilitating issues that point directly to a failing Transmission Control Module (TCM). As the electronic brain of your automatic transmission, a faulty TCM can make your reliable SUV feel unpredictable and unsafe. This is a direct-fit, VIN-programmed T42 TCM, part number 24238856, designed to restore the crisp, smooth shifting you expect from your vehicle.
Case Study: A Tricky Diagnosis
I had a 2008 Envoy in my bay last month that was giving the owner fits. The complaint was intermittent harsh shifting and occasionally getting stuck in 3rd gear, but only after driving for 30+ minutes on a hot day. We couldn’t replicate the issue on short test drives. After checking fluid levels and scanning for codes (we found a stored P0700), we suspected the TCM. These modules, often mounted in the engine bay, are prone to failure from years of heat cycles. The internal circuits develop micro-fractures that only cause problems when the module gets hot and expands. Swapping in a pre-programmed TCM like this one solved the problem instantly. It’s a classic failure mode I’ve seen hundreds of times on these GM platforms.
Is Your GMC Envoy Showing These Transmission Warning Signs?
A failing TCM doesn’t always mean a complete transmission failure. Often, the signs are electronic. If you’re experiencing any of the following, your TCM is the most likely culprit for your 2006-2009 Envoy TCM issues:
- ✔ Harsh, banging shifts or delayed gear engagement.
- ✔ The vehicle is stuck in “limp mode” and won’t shift out of a single gear (usually 2nd or 3rd).
- ✔ The Check Engine Light or a specific transmission warning light is illuminated.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700 (Transmission Control System Malfunction), P0750, or other solenoid-specific codes.
- ✔ A noticeable drop in fuel economy due to inefficient shifting.
- ✔ Complete loss of communication with the transmission module.
Your Step-by-Step Guide to a Quick Installation
One of the best features of this module is its straightforward installation. You don’t need a professional lift or specialized transmission tools. For most DIYers, this is a job that can be completed in under 30 minutes with basic hand tools.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electronic component replacement.
- Locate the Module: On the GMC Envoy, the TCM is typically found in the engine compartment on the driver’s side (LH side).
- Disconnect and Remove: Carefully unplug the electrical connectors. Be gentle with the locking tabs, as they can become brittle over time. Then, unbolt the old module from its mounting bracket.
- Install the New TCM: Mount the new module in the same location and securely fasten it. Reconnect the electrical harnesses, ensuring they click into place.
- Final Steps: Reconnect the battery terminal. While our VIN programming handles the critical setup, it’s always good practice to use a basic OBD2 scan tool to clear any old stored fault codes from the vehicle’s memory.
Verified Fitment for Your General Motors Vehicle
While this is a perfect solution for the 2006-2009 Envoy TCM, this T42 module is also compatible with a wide range of other GM cars, trucks, and SUVs equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. It is a direct replacement for multiple part numbers, including 24252114, 24234503, and 24238856.
This part is confirmed to fit models such as:
- GMC Envoy / Envoy XL (2006-2009)
- Chevrolet Trailblazer (2006-2009)
- Chevrolet Silverado & GMC Sierra 1500/2500 (2007-2013)
- Chevrolet Tahoe & GMC Yukon (2007-2009)
- Chevrolet Impala (2006-2011)
- Cadillac DTS (2006-2011)
- Hummer H3 (2008-2010)
- Pontiac G6 / Grand Prix (2006-2010)
- And many more. Please verify your specific model in the fitment list.
Frequently Asked Questions
What does VIN programming mean for me?
It means this module arrives ready for installation. We flash it with your vehicle’s specific VIN and the latest GM software before shipping. This eliminates the need for an expensive trip to the dealership for programming, saving you time and money. It’s a true plug-and-play solution.
Is this a difficult part to replace myself?
Not at all. For most vehicle owners with basic hand tools, this is a very manageable DIY job. The module is located in the engine bay, making it easily accessible without lifting the vehicle. The entire process typically takes less than half an hour.
Will this fix a P0700 trouble code?
A P0700 code is a general fault code indicating the TCM has detected a problem. While this module often resolves the root cause of a P0700, it’s important to have the vehicle scanned for more specific codes (like solenoid or sensor faults) to confirm the diagnosis. In many cases, a failing TCM is the primary culprit.
Do I need to return my old TCM?
No, there is no core charge for this part. You can keep your old module or dispose of it responsibly without any hassle or need to ship it back.