Is your 2006-2009 Chevrolet Trailblazer suffering from unpredictable shifting, getting stuck in gear, or throwing transmission codes? These are classic signs of a failing Transmission Control Module (TCM). As the electronic brain of your 4L60E or 4L70E transmission, a faulty TCM can make your reliable SUV feel unsafe and unpredictable. Stop chasing intermittent electrical ghosts and get a definitive fix with our VIN-programmed T42 TCM, a direct replacement for part number 24238856.
For over 20 years, I’ve seen drivers and shops struggle with modules that require expensive dealer tools for programming. We eliminate that step entirely. By providing your vehicle’s VIN at checkout, we program the module with the latest GM software before it even ships. This ensures it communicates perfectly with your vehicle’s engine computer and other systems right out of the box. This isn’t just a part; it’s a complete, ready-to-install solution for your 2006-2009 Trailblazer TCM issues.
Is Your Trailblazer Exhibiting These Telltale Signs?
- ✔ Harsh, banging shifts or delayed gear engagement.
- ✔ Vehicle is stuck in “limp mode,” usually in 2nd or 3rd gear.
- ✔ The Check Engine Light or a transmission warning light is on.
- ✔ Diagnostic Trouble Codes (DTCs) like P0700, P0753, P0758, or other solenoid-related faults are present.
- ✔ A noticeable drop in fuel economy or a feeling of sluggish performance.
- ✔ Complete loss of communication with the TCM, preventing shifting.
A Technician’s Notebook
I remember a 2008 Trailblazer that came into the shop with a textbook case of TCM failure. The owner complained of intermittent harsh 1-2 shifts and the occasional P0753 (Shift Solenoid ‘A’ Electrical) code. He’d already replaced the solenoid, but the problem persisted. After confirming the wiring harness was good, we knew the culprit was the module itself. Heat cycles and vibration had caused an internal solder joint to fail, creating an intermittent open circuit. A replacement 2006-2009 Trailblazer TCM, programmed and installed in under 30 minutes, permanently solved the problem. It’s a repair I’ve done hundreds of times on these GM platforms.
A Straightforward Guide to Installation
You don’t need to be a master mechanic to replace this module. The entire process typically takes less than 30 minutes with basic hand tools.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery to prevent electrical shorts and help reset the vehicle’s systems.
- Locate the TCM: On the 2006-2009 Trailblazer, the TCM is conveniently located 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 connectors. You should hear a ‘click’ as they lock in.
- Reconnect and Verify: Reconnect the battery terminal. Start the vehicle and ensure the check engine light is off and the transmission shifts smoothly. We recommend using a basic scan tool to clear any stored historical codes.
Verified Vehicle Compatibility
This T42 TCM, part number 24238856, is a direct replacement for a wide range of General Motors vehicles. While this page is focused on the 2006-2009 Trailblazer TCM, it also fits the following models. Please verify your specific model and location notes.
- TRAILBLAZER 06-09 Transmission; (LH engine compartment)
- ENVOY 06-09 Transmission; (LH engine compartment)
- RAINIER 06-07 Transmission
- SAAB 9-7X 06-09 Transmission; (LH engine compartment)
- SILVERADO & SIERRA 1500/2500 07-13 Transmission; (next to battery)
- TAHOE & YUKON 07-09 Transmission; (next to battery)
- SUBURBAN & YUKON XL 1500 07-08 Transmission; (next to battery)
- AVALANCHE 1500 07-08 Transmission; (next to battery)
- EXPRESS & SAVANA VANS 06-14 Transmission; (RH engine compartment)
- IMPALA 06-11 Transmission; (lower air cleaner housing)
- GRAND PRIX 06-08 Transmission; (lower air cleaner housing)
- LACROSSE / ALLURE 06-09 Transmission; (lower air cleaner housing)
- COBALT / G5 / PURSUIT 06-10 Transmission; (LH strut tower)
- HHR 06-11 Transmission; (LH engine compartment)
- HUMMER H3 08-10 Transmission; (RH rear engine compartment)
- And many more. Check the full list to confirm your vehicle.
Frequently Asked Questions
Do I need to do any programming or flashing myself?
No. This module is sold as a plug-and-play solution. We handle all the programming to your vehicle’s VIN before we ship it, so it’s ready for installation right out of the box. This saves you a trip to the dealership.
Is a core charge required for this part?
No, there is no core charge. You can keep your old part, so you don’t have to worry about the cost or hassle of shipping it back.
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. This code is almost always accompanied by more specific transmission codes (like P0753). Replacing a faulty TCM will resolve the underlying issue, which in turn will clear the P0700 code.
Where is the TCM located on my 2007 Trailblazer?
On the 2006-2009 Trailblazer, the Transmission Control Module is typically found in the engine bay, mounted on the driver’s side (LH) inner fender or near the firewall.