Restore Smooth Shifting to Your GMC Envoy
If your 2006-2009 GMC Envoy is experiencing unpredictable shifting, getting stuck in gear, or throwing transmission codes, the culprit is often a failing Transmission Control Module (TCM). As a technician with over two decades of experience, I’ve seen countless drivers worry about a complete transmission failure when the real issue was this small electronic brain. This T42 TCM, part number 24241806, is the direct-fit, reliable solution to get your SUV driving like new again, without the astronomical cost of a dealership visit.
A Technician’s Notebook: The Misleading P0753 Code
A customer brought in a 2008 Envoy that wouldn’t shift past second gear—classic limp mode. The dash was lit up with a Check Engine light, and a quick scan pulled a P0753, indicating a “Shift Solenoid ‘A’ Electrical” fault. A less experienced mechanic might immediately start dropping the transmission pan to replace the solenoid. However, after seeing hundreds of these GM vehicles, my first step is to check the TCM. The internal drivers on these T42 modules are known to fail, creating an open circuit that mimics a bad solenoid. We swapped in a pre-programmed TCM, cleared the codes, and the Envoy shifted perfectly. A 30-minute fix saved the customer over a thousand dollars and a day of shop time.
Is Your Envoy Exhibiting These Telltale Symptoms?
A faulty TCM can manifest in several ways, often mistaken for more severe mechanical problems. Here’s what to look for:
- ✔ Harsh, jerky, or delayed gear shifts.
- ✔ The vehicle is stuck in a single gear (limp mode), usually 2nd or 3rd.
- ✔ Check Engine Light or Transmission Warning Light is on.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750-P0758, or other solenoid-related faults.
- ✔ Complete loss of upshifting or downshifting capability.
- ✔ A noticeable drop in fuel economy.
- ✔ Intermittent communication loss with the transmission.
A Straightforward Guide to Your TCM Installation
Replacing the 2006-2009 Envoy TCM is a job most DIYers can handle in their own garage. Because this module comes pre-programmed to your vehicle’s VIN, you can skip the expensive trip to the dealer for programming.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery to prevent electrical shorts and help reset the system.
- Locate the Module: On the GMC Envoy and its platform siblings (like the Trailblazer and Saab 9-7X), the TCM is typically found in the engine compartment on the driver’s side (LH).
- 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 securely onto the bracket and firmly reconnect the electrical harnesses. You should hear a click as they lock into place.
- Final Steps: Reconnect the battery terminal. Start the vehicle and use a basic OBD2 scan tool to clear any lingering fault codes from the computer’s memory. Take a test drive to confirm smooth shifting.
Verified Fitment for Your General Motors Vehicle
This T42 TCM is a direct replacement for part number 24241806 and is compatible with a wide range of GM vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. Please verify your model and location below:
- ENVOY 06-09: Transmission; (LH engine compartment)
- TRAILBLAZER 06-09: Transmission; (LH engine compartment)
- SAAB 9-7X 06-09: Transmission; (LH engine compartment)
- CHEVROLET SILVERADO / GMC SIERRA 1500 07-13: Transmission; (next to battery), check for new body style in ’07
- CHEVROLET TAHOE / GMC YUKON 07-09: Transmission; (next to battery)
- CHEVROLET AVALANCHE 1500 07-08: Transmission; (next to battery)
- CHEVROLET EXPRESS / GMC SAVANA VANS 06-14: Transmission; (RH engine compartment)
- HUMMER H3 08-10: Transmission; (RH rear engine compartment)
- And many more GM cars, trucks, and SUVs.
Frequently Asked Questions
Do I need to get this module programmed by a dealer?
No. We program the module to your vehicle’s specific VIN before shipping. It arrives ready for a true plug-and-play installation, saving you time and money.
What is a T42 TCM?
The T42 is the hardware platform name for this generation of General Motors Transmission Control Module. It’s the electronic controller responsible for all automatic shifting functions.
Will this fix a P0700 trouble code?
A P0700 code is a general fault request from the TCM to the Engine Control Module (ECM) to turn on the Check Engine Light. While this module can resolve the underlying issue causing the P0700, you should scan for other ‘P’ codes to pinpoint the exact transmission fault.
Is there a core charge for my old part?
No, there is no core charge. You can keep your old module or dispose of it without the hassle of sending it back.
What if my part number is slightly different?
This module, 24241806, interchanges with many other GM service numbers like 24252114, 24234503, and 24242391. As long as your vehicle is on the compatibility list, this programmed module will function correctly.