Is Your Trailblazer’s Transmission Acting Up?
If you’re dealing with a 2006-2009 Chevrolet Trailblazer that’s shifting harshly, getting stuck in gear, or throwing transmission-related codes, the problem is very likely a failing Transmission Control Module (TCM). As the electronic brain of your automatic transmission, the T42 TCM is responsible for every shift command. When it fails, it can cause a host of drivability issues that range from annoying to downright unsafe. Over my 20 years in diagnostics, I’ve seen countless GM vehicles, especially trucks and SUVs like the Trailblazer, come into the shop with these exact symptoms. The cause is often internal circuit failure within the original module due to heat and vibration over time.
This replacement T42 module, part number 24230461, is the definitive solution. We take the guesswork and hassle out of the repair by pre-programming it to your vehicle’s specific VIN. This means it arrives ready for a true plug-and-play installation, restoring the crisp, predictable shifting you expect from your vehicle without a mandatory trip to the dealership for expensive programming.
Case Study: A Tricky Diagnosis
A customer brought in their ’08 Trailblazer complaining of intermittent ‘limp mode’—it would get stuck in 3rd gear—and a check engine light. They had already replaced two shift solenoids based on the codes, but the problem persisted. My scan tool showed a P0700 (Transmission Control System Malfunction) and intermittent communication loss with the TCM. Instead of just throwing more parts at it, we checked the wiring harness for integrity—it was fine. This pointed directly to an internal fault in the TCM itself. After installing one of our VIN-programmed modules, all codes were cleared, and the transmission shifted perfectly on the test drive. The customer was relieved to have a final, reliable fix that didn’t involve more guesswork.
Is Your Trailblazer Exhibiting These Telltale Signs?
- ✔ Harsh, banging shifts or delayed gear engagement.
- ✔ Vehicle is stuck in one gear (often called “limp mode”).
- ✔ Check Engine Light is on with codes like P0700, P0750, or other solenoid-related DTCs.
- ✔ Inability to upshift or downshift properly, leading to poor acceleration.
- ✔ A noticeable drop in fuel economy as the transmission operates inefficiently.
- ✔ Complete loss of communication with the transmission module.
A Straightforward Guide to Installation
For the DIY mechanic, this is a very manageable job. On the 2006-2009 Trailblazer, the TCM is typically easy to access. You’ll have your vehicle back to normal in under an hour.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electronic work.
- Locate the Module: On the Trailblazer and its platform-mates (like the Envoy), the TCM is located 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. 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. You should hear a ‘click’ as they lock in.
- Final Steps: Reconnect the battery terminal. Start the vehicle and use a basic OBD-II scan tool to clear any stored fault codes from the ECU. Take the vehicle for a test drive to confirm smooth operation.
Verified Vehicle Compatibility
This module is a direct replacement for part number 24230461 and other service numbers. While this page focuses on the 2006-2009 Trailblazer TCM, it also fits a wide range of other GM vehicles. Please verify your specific model in the list below.
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 more GM cars, trucks, and SUVs. Please see the full list provided.
Frequently Asked Questions
Do I need to get this programmed by a dealer?
No. This module comes fully programmed to your vehicle’s VIN number. It is ready for installation right out of the box, saving you time and money.
What does ‘plug-and-play’ mean?
It means you simply remove your old, faulty module and install this one. No special software, tools, or procedures are required to make it work with your vehicle.
Is this compatible with the 4L60E transmission in my Trailblazer?
Yes, this T42 TCM is the correct controller for GM vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E during these model years.
Where is the TCM located on a 2007 Trailblazer?
On the 2006-2009 Trailblazer, the Transmission Control Module is located in the engine bay, on the left-hand (driver’s side) inner fender or firewall area.
What is the warranty on this part?
This part comes with a one-year warranty, giving you peace of mind that you’re installing a quality, reliable component.