If your 2006-2009 GMC Envoy is suffering from erratic shifting, getting stuck in gear, or throwing transmission codes, you’re not alone. As a technician with over two decades of experience, I’ve seen countless GM vehicles sidelined by a failing Transmission Control Module (TCM). The TCM is the electronic brain of your automatic transmission, and when it malfunctions, it can cause a host of frustrating and potentially damaging problems. This VIN-programmed T42 TCM, part number 24243921, is the definitive solution to restore your vehicle’s smooth, reliable performance without an expensive trip to the dealership.
This isn’t just a replacement part; it’s a complete, ready-to-install fix. We pre-program each module to your vehicle’s specific VIN, loading the latest GM software updates. This ensures perfect communication between the engine and transmission, optimizing shift points, torque converter clutch engagement, and fuel efficiency right out of the box. You get a component that meets or exceeds original equipment standards for a fraction of the dealer price.
From the Diagnostic Bay: A Common Envoy Case
I remember a customer bringing in his ’07 Envoy. He was frustrated because it would intermittently refuse to shift out of 2nd gear, and the check engine light was on. His local shop had already replaced a shift solenoid with no success. After a quick scan, I saw the classic P0700 (Transmission Control System Malfunction) code. Instead of chasing more mechanical ghosts, we identified the root cause: the original TCM was failing. We installed a VIN-programmed module just like this one, and in under an hour, the Envoy was shifting perfectly. The customer saved hundreds on diagnostics and got a lasting repair.
Is Your Envoy Exhibiting These Telltale Signs?
A faulty TCM can manifest in several ways. If you’re noticing any of the following, it’s a strong indicator that your module needs attention. This part is engineered to resolve these exact issues:
- ✔ Harsh, slamming shifts or delayed gear engagement.
- ✔ Vehicle is stuck in “limp mode” (usually 2nd or 3rd gear).
- ✔ Check Engine Light or Transmission Warning Light is illuminated.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750, or other solenoid-related faults.
- ✔ Inability to upshift or downshift correctly, leading to poor acceleration.
- ✔ A sudden drop in fuel economy or signs of the transmission overheating.
A Straightforward Guide to Installation
One of the best features of this part is its simple, plug-and-play installation. No special tools are required, and most DIY mechanics can complete the job in under 30 minutes. Here’s a general guide for replacing your 2006-2009 Envoy TCM:
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- Locate the Module: On the GMC Envoy and similar platforms (like the Trailblazer or Saab 9-7X), the TCM is typically found in the engine compartment on the driver’s side (LH side).
- Disconnect and Remove: Carefully unplug the electrical connectors from the old module. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, pre-programmed TCM into place and securely reconnect the electrical harnesses. Ensure they click into place.
- Final Steps: Reconnect the battery terminal. While our programming handles the critical setup, it’s good practice to use a basic scan tool to clear any stored fault codes from the vehicle’s memory.
Verified Vehicle Compatibility
This T42 TCM is a direct-fit replacement for a wide range of General Motors vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. While it is a perfect solution for the 2006-2009 Envoy TCM, it also fits many others. Please verify your part number (24243921) or consult the list below.
This part fits these makes and models with these options:
GMC ENVOY 2006-2009 Transmission; (LH engine compartment)
CHEVROLET TRAILBLAZER 2006-2009 Transmission; (LH engine compartment)
SAAB 9-7X 2006-2009 Transmission; (LH engine compartment)
…and many other GM cars, trucks, and SUVs from 2006-2014. See the full fitment list provided in the initial data for extensive compatibility.
Frequently Asked Questions
Does this module really not require a trip to the dealer for programming?
That’s correct. We handle all the programming here before we ship it. Just provide your vehicle’s VIN during checkout, and the module will arrive ready for plug-and-play installation, saving you time and money.
What tools do I need for installation?
Basic hand tools are all that’s required. Typically, you’ll just need a socket set to unbolt the module and disconnect the battery. No specialized diagnostic equipment is needed for the installation itself.
Is there a core charge for my old part?
No, there is absolutely no core charge. You can keep your old module or dispose of it at your convenience without the hassle of returning it.
How can I be sure the TCM is the problem and not something else?
While symptoms like harsh shifting can have multiple causes, the combination of these symptoms with specific transmission-related DTCs (like P0700) strongly points to a faulty TCM. This module is designed to be the definitive fix for these electronic failures.
What kind of warranty is included?
We stand behind our products with a one-year warranty, giving you peace of mind that you’re investing in a quality, reliable component for your vehicle.