If your 2006-2009 Chevrolet Trailblazer is suffering from erratic shifting, getting stuck in gear, or throwing transmission codes, you’ve come to the right place. As a technician with over two decades of experience, I’ve seen firsthand how a failing Transmission Control Module (TCM) can bring an otherwise solid SUV to a halt. This isn’t just an annoyance; it’s a critical failure that compromises your vehicle’s performance and safety. This T42 TCM, corresponding to part number 24239926, is the definitive solution to restore the crisp, predictable shifting you expect from your vehicle.
The TCM is the brain of your automatic transmission, constantly analyzing data from engine speed, vehicle speed, and throttle position to command precise gear changes and torque converter lockup. When it fails, the communication breaks down, leading to the frustrating symptoms you’re likely experiencing. Our module is the answer, arriving at your door fully programmed to your Trailblazer’s specific Vehicle Identification Number (VIN). This means no expensive trips to the dealership for programming—it’s a true plug-and-play fix that you or your mechanic can perform quickly.
Case Study: A Tricky Diagnosis
I remember a 2008 Trailblazer that came into my shop with a complaint of intermittent, violent 1-2 shifts and occasionally getting stuck in 3rd gear (limp mode). The owner had already replaced two shift solenoids at another shop with no success. A scan showed a generic P0700 code. Instead of just throwing more parts at it, we looked at live data. We noticed the command signals from the TCM were dropping out randomly. The root cause wasn’t a mechanical fault inside the transmission, but the TCM itself suffering from internal circuit board failure. We installed a VIN-programmed module, and the problem was solved instantly. This is a classic scenario where correctly diagnosing the TCM saves hundreds in wasted parts and labor.
Is Your Trailblazer 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 replacement:
- ✔ Harsh, delayed, or unpredictable gear shifts.
- ✔ The vehicle is stuck in a single gear (often called “limp mode”).
- ✔ Check Engine Light or Transmission Warning Light is illuminated with codes like P0700, P0750, or other solenoid-related faults.
- ✔ Failure to upshift or downshift properly.
- ✔ A noticeable decrease in fuel economy.
- ✔ Inability to communicate with the TCM using a diagnostic scan tool.
A Straightforward Guide to Your TCM Replacement
Installing your new 2006-2009 Trailblazer TCM is a job most DIY enthusiasts can handle in under an hour with basic hand tools. For the 2006-2009 Trailblazer, the TCM is typically located in the left-hand (driver’s side) engine compartment.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the system.
- Locate the Module: Find the TCM on the driver’s side of the engine bay. It’s a silver box with electrical connectors.
- Disconnect and Remove: Carefully unplug the wiring harness connectors. Press the release tabs firmly. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, VIN-programmed TCM into place. Reconnect the wiring harnesses, ensuring they click securely into place.
- Final Steps: Reconnect the battery terminal. While our programming handles the critical setup, it’s good practice to use a basic OBD2 scanner to clear any stored diagnostic trouble codes (DTCs) from the vehicle’s memory. Start the engine and take a test drive to confirm smooth shifting.
Verified Vehicle Compatibility List
This module is a direct replacement for part number 24239926 and other interchangeable numbers. It is specifically programmed for the following vehicle:
- Chevrolet Trailblazer (2006, 2007, 2008, 2009) – Located in the LH engine compartment. Also fits 8-cylinder models from 2006-2007 and the EXT model from 2006.
While this part fits a wide range of GM vehicles, this listing is specifically for the Trailblazer. Please verify your part number or contact us with your VIN to ensure 100% compatibility.
Frequently Asked Questions
Do I need to have this TCM programmed by a dealer?
No. This is the biggest benefit we offer. We program the module to your vehicle’s VIN before shipping. It arrives ready for installation, saving you time and the high cost of dealership programming.
What information do you need from me to program it?
We require your vehicle’s 17-digit VIN (Vehicle Identification Number) at checkout. This ensures we can load the correct factory software for your specific Trailblazer configuration.
Is there a core charge for my old part?
No, there is no core charge. You can keep your old part or recycle it locally without the hassle of shipping it back to us.
What kind of warranty is included?
This module is backed by our one-year, hassle-free warranty, giving you peace of mind with your purchase.
Will this fix a P0700 trouble code?
A P0700 code is a general fault request from the TCM to the main engine computer. While a faulty TCM is a very common cause for this code, it’s essential to have the vehicle scanned for more specific transmission codes (e.g., P07xx series) to confirm the diagnosis. In many cases, replacing a failed TCM will resolve the P0700 code.