Restore Peak Transmission Performance in Your Trailblazer
As a technician with over two decades of experience under the hood, I’ve seen countless GM vehicles, especially the 2006-2009 Trailblazer, come into the shop with frustrating transmission issues. More often than not, the culprit is a failing Transmission Control Module (TCM). If your SUV is suffering from harsh shifting, getting stuck in gear, or throwing transmission-related codes, you’ve found the reliable, long-term solution. This T42 TCM, part number 24243921, is the brain of your automatic transmission, and replacing a faulty one is the key to getting your vehicle driving like new again.
This isn’t just a replacement part; it’s a complete solution. We pre-program each module to your vehicle’s specific VIN before it ships. This crucial step ensures it communicates flawlessly with your Engine Control Module (ECM) and other vehicle systems right out of the box. You get the benefit of the latest GM software updates without the expensive trip to the dealership for programming. This is the definitive fix for your 2006-2009 Trailblazer TCM problems, designed for both seasoned mechanics and first-time DIYers.
Case Study: A Tricky Diagnosis
I once had a 2008 Trailblazer come in with what the owner described as ‘random, violent shifts’ and an intermittent check engine light. The codes were all over the place—solenoid performance, lost communication, you name it. We checked the wiring and fluid levels, which were fine. The issue seemed electrical and inconsistent. After swapping in a known-good, VIN-programmed T42 TCM, every single issue vanished. The root cause wasn’t a mechanical failure inside the transmission but a faulty module creating electronic chaos. This experience solidified for me how critical a properly functioning TCM is for the entire drivetrain.
Common Signs of a Failing TCM
- ✔ Check Engine Light or Transmission Warning Light is on, often with codes like P0700, P0750, P0753, or other solenoid-specific faults.
- ✔ Harsh, erratic, or delayed gear shifts that make driving uncomfortable and unpredictable.
- ✔ Vehicle enters “limp mode,” getting stuck in a single gear (usually 2nd or 3rd) to protect the transmission.
- ✔ Failure to upshift or downshift, resulting in poor acceleration and terrible fuel economy.
- ✔ The gear selector indicator (P-R-N-D) on the dash may be blank or incorrect.
- ✔ Complete loss of communication with the scan tool, or intermittent connection problems.
A Straightforward Guide to Installation
Replacing the 2006-2009 Trailblazer TCM is a job most people can handle in their own driveway in under 30 minutes. No specialized tools are required.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the vehicle’s computer systems.
- Locate the Module: On the 2006-2009 Trailblazer, the TCM is typically found in the engine compartment on the driver’s side (LH side).
- Disconnect and Remove: Carefully unclip the wiring harness connectors from the old TCM. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, VIN-programmed TCM into place. Reconnect the wiring harness connectors, ensuring they click securely into position.
- Final Steps: Reconnect the negative battery terminal. While our programming handles the critical setup, it’s good practice to use a basic OBD2 scan tool to clear any stored fault codes. Start the vehicle and enjoy smooth shifting!
Verified Vehicle Compatibility
This module is a direct-fit replacement for the T42 TCM in a wide range of General Motors vehicles. While this page is focused on the Trailblazer, please confirm your model and year from the list below. This part is interchangeable with service numbers 24242391, 24234503, 24252114, and others.
This part will fit these makes and models with these options:
TRAILBLAZER 06-07 Transmission; (LH engine compartment), (8 cylinder)
TRAILBLAZER 08-09 Transmission; (LH engine compartment)
TRAILBLAZER EXT 06 Transmission; (LH engine compartment), (8 cylinder)
ENVOY 06-07 Transmission; (LH engine compartment), (8 cylinder)
ENVOY 08-09 Transmission; (LH engine compartment)
ENVOY XL 06 Transmission; (LH engine compartment), (8 cylinder)
RAINIER 06-07 Transmission
SAAB 9-7X 06-09 Transmission; (LH engine compartment)
… and many other GM cars, trucks, and SUVs from 2006-2014. Please verify your specific application.
Frequently Asked Questions
Do I need to take this part to a dealer for programming?
No. This is the biggest benefit of our service. We program the module to your vehicle’s VIN before we ship it. It arrives ready for a plug-and-play installation, saving you time and the high cost of dealership programming.
Is this a new or used part?
This is a high-quality, OEM-standard replacement part built to meet or exceed original specifications for performance and longevity. It is backed by our one-year warranty for your peace of mind.
Will this fix a P0700 trouble code?
A P0700 code is a general transmission fault request from the TCM to the ECM to turn on the check engine light. It means the TCM has stored more specific codes. If the root cause is a faulty module, replacing it with our programmed 2006-2009 Trailblazer TCM will resolve the P0700 and the underlying codes.
Where is the TCM located on my 2007 Trailblazer?
On the 2006-2009 Trailblazer models, the Transmission Control Module is located in the engine bay, typically mounted on the driver’s side (LH) inner fender or firewall area.
What if I order the wrong part?
We encourage you to verify your part number and vehicle fitment before ordering. However, we have an expert support team and a straightforward return policy to help you get the correct part for your vehicle if a mistake is made.