If you’re dealing with a 2006 Trailblazer EXT that’s shifting erratically, getting stuck in gear, or throwing transmission codes, you’ve come to the right place. As a technician with over two decades of experience under the hood, I’ve seen countless GM vehicles sidelined by a faulty Transmission Control Module (TCM). The T42 module, specifically, is the brain of your automatic transmission, and when it fails, it can cause a cascade of frustrating and potentially damaging problems. This isn’t just a part; it’s the solution to get your SUV driving smoothly and reliably again.
This OEM-quality T42 TCM, part number 24235340, is the definitive fix for these issues. We take the guesswork and dealership hassle out of the equation. Before we ship it, we program the module to your vehicle’s specific VIN. This ensures it communicates perfectly with your engine computer and other systems right out of the box. No expensive trips to the dealer for programming, no special tools—just a straightforward replacement that restores factory performance.
A Technician’s Notebook: The Misleading Solenoid Code
I remember a 2006 Trailblazer EXT that came into the shop a few years back. The owner was frustrated; he’d already replaced a shift solenoid based on a P0750-series code, but the harsh 1-2 shift and intermittent ‘limp mode’ persisted. His scanner kept pointing to the solenoid. After checking the wiring and finding no issues, my experience pointed me to the TCM. On these GM platforms, a failing T42 module can send faulty signals, incorrectly flagging good components. We swapped in a VIN-programmed TCM, cleared the codes, and the truck shifted like new. It’s a classic case where the root cause isn’t the component being flagged, but the computer controlling it. This module solves that core problem.
Diagnosing a Faulty 2006 Trailblazer EXT TCM
A failing transmission computer can manifest in several ways. If your Trailblazer is experiencing any of the issues below, a faulty TCM is a very likely culprit. In my shop, heat and vibration are the top two reasons these modules fail, leading to internal circuit board issues that cause these exact symptoms.
- ✔ ✔ Harsh, jerky, or delayed gear shifts that make driving uncomfortable.
- ✔ ✔ The vehicle is stuck in a single gear (often 2nd or 3rd), a condition known as “limp mode.”
- ✔ ✔ Your Check Engine Light or a dedicated transmission warning light is illuminated.
- ✔ ✔ You’ve pulled Diagnostic Trouble Codes (DTCs) like P0700 (Transmission Control System Malfunction), P0750, P0753, or other solenoid-related codes.
- ✔ ✔ A noticeable drop in fuel economy as the transmission isn’t operating efficiently.
- ✔ ✔ Complete loss of communication with the module, preventing the vehicle from starting or shifting out of Park.
Simple Steps for a Successful Installation
One of the best parts about this solution is its simplicity. For a DIYer with basic tools, this is a job you can complete in your driveway in less than an hour. Here’s a straightforward guide to get it done.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work. This prevents short circuits and helps reset the vehicle’s electronic systems.
- Locate the TCM: On your 2006 Trailblazer EXT, the TCM is typically found in the engine compartment on the driver’s side (LH engine compartment). It’s a silver box with electrical connectors.
- Disconnect and Remove: Carefully unplug the electrical harnesses from the old module. Press the release tabs firmly. Then, unbolt the module from its mounting bracket.
- Install the New Module: Mount your new, VIN-programmed TCM onto the bracket and securely tighten the bolts. Reconnect the electrical harnesses, ensuring they click into place.
- Final Steps: Reconnect the negative battery terminal. While the module is plug-and-play, it’s good practice to use a basic OBD-II scan tool to clear any stored fault codes from the previous issue. Start the vehicle and take it for a test drive to confirm smooth shifting.
Verified Vehicle Compatibility
This module is a direct replacement for part number 24235340 and other service numbers. It is designed for a wide range of GM vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. While this page focuses on the Trailblazer EXT, please confirm your vehicle is on the list below.
This part will fit these makes and models with these options:
TRAILBLAZER EXT 06 Transmission; (LH engine compartment), (8 cylinder)
ENVOY 06-09 Transmission; (LH engine compartment)
EXPRESS VANS (1500/2500/3500) 06-14 Transmission; (RH engine compartment)
SAVANA VANS (1500/2500/3500) 06-14 Transmission; (RH engine compartment)
SIERRA & SILVERADO (1500/2500) 07-13 Transmission; (next to battery)
TAHOE & YUKON 07-09 Transmission; (next to battery)
… and many more GM cars, trucks, and SUVs. Please see the full fitment list provided.
Frequently Asked Questions
What exactly is VIN programming and why do I need it?
VIN programming loads your vehicle’s unique identification number and factory-specific software onto the TCM. This ensures the module works perfectly with your engine, transmission type, and options. Without it, the vehicle may not start, shift correctly, or may display error messages. Our service handles this for you, so it’s ready for installation upon arrival.
Do I need to take my vehicle to a dealership after installation?
No. Because this module comes pre-programmed to your VIN, you do not need to visit a dealership or repair shop for additional programming. This saves you time and the typical dealer service fee, which can be hundreds of dollars.
Is there a core charge for my old part?
No, there is no core charge required for this part. You can keep your old module or dispose of it without the hassle of returning it, simplifying your repair process.
Will this fix a P0700 trouble code?
A P0700 code is a general fault code indicating the TCM has detected a problem. While this module often resolves the underlying issue causing the P0700, it’s crucial to diagnose any other specific codes that are present (e.g., solenoid or sensor codes). In many cases I’ve diagnosed, a faulty TCM was the root cause triggering the P0700 and other related codes.