Fix Your GM Transmission Problems for Good
If you’re dealing with a transmission that seems to have a mind of its own—slamming into gear, refusing to shift, or putting your 2006 Trailblazer EXT into a frustrating ‘limp mode’—you’ve come to the right place. As a technician with over two decades of experience, I’ve seen countless GM vehicles sidelined by a faulty Transmission Control Module (TCM). The T42 module, specifically, is the electronic brain of your automatic transmission, and when it fails, it causes chaos. This isn’t just an inconvenience; it’s a safety and reliability issue. This direct-replacement 2006 Trailblazer EXT TCM, part number 24243921, is the definitive solution, pre-programmed to your vehicle’s VIN for a hassle-free, plug-and-play installation.
A Technician’s Notebook: The Limp Mode Trailblazer
A customer brought in his 2006 Trailblazer EXT, complaining it was stuck in 3rd gear. He’d already been to another shop that quoted him thousands for a complete transmission rebuild. He was frustrated and ready to sell the truck. I pulled the codes and saw a generic P0700 (Transmission Control System Malfunction) and a specific solenoid circuit code. Instead of tearing into the transmission, I checked the TCM. In my shop, I’ve diagnosed hundreds of these T42 failures caused by years of heat cycles and engine vibration, which weaken internal solder joints. We swapped in a VIN-programmed module just like this one, and in less than an hour, the truck was shifting perfectly. He saved a fortune and kept the vehicle he loved. This module is often the simple fix to what seems like a catastrophic failure.
Is Your Trailblazer Exhibiting These Telltale Signs?
A failing TCM doesn’t always mean a complete shutdown. It often starts with subtle but annoying symptoms. If your vehicle is experiencing any of the following, a faulty TCM is the likely culprit. Ignoring these can lead to permanent transmission damage.
- ✔ Harsh, erratic, 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.”
- ✔ The Check Engine Light or a dedicated transmission warning light is illuminated on your dash.
- ✔ Your scan tool shows Diagnostic Trouble Codes (DTCs) like P0700, P0750, or other solenoid-related faults.
- ✔ A sudden and unexplained drop in fuel economy.
- ✔ The transmission feels like it’s slipping or failing to engage properly when you accelerate.
Your 30-Minute Path to a Smooth Ride
One of the best features of this module is that it’s designed for a straightforward DIY installation. You don’t need a lift or specialized transmission tools—just basic hand tools and about 30 minutes. Getting your 2006 Trailblazer EXT TCM installed is a simple process.
- 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 Module: On the 2006 Trailblazer EXT, the TCM is typically found in the engine compartment on the left-hand (driver’s) side. Check near the firewall or inner fender.
- Swap the Part: Carefully unplug the electrical connectors. Be gentle with the locking tabs, as they can become brittle over time. Unbolt the old module from its bracket, set the new one in its place, secure the bolts, and reconnect the electrical harnesses.
- Finalize the Fix: Reconnect the battery terminal. Start the vehicle and let it run for a moment. While our VIN programming handles the critical setup, it’s always good practice to use a basic OBD2 scan tool to clear any stored fault codes from the ECU’s memory.
Verified Fitment for Your General Motors Vehicle
This T42 TCM is a direct replacement for part number 24243921 and is compatible with a wide range of GM vehicles. Please verify your model and options below.
This part will fit these makes and models with these options:
TRAILBLAZER EXT 06 Transmission; (LH engine compartment), (8 cylinder)
ALLURE 06-09 Transmission; (lower air cleaner housing)
AURA 07-09 Transmission; (LH frame rail front)
AVALANCHE 1500 07-08 Transmission; (next to battery)
CANYON 08-12 Transmission; (RH rear engine compartment)
COBALT 06-10 Transmission; (LH strut tower)
COLORADO 08-12 Transmission; (RH rear engine compartment)
DTS 06-11 Transmission; (RH front engine compartment)
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)
EXPRESS 1500 VAN 06-14 Transmission; (RH engine compartment)
EXPRESS 2500 VAN 06-14 Transmission; (RH engine compartment)
EXPRESS 3500 VAN 06-14 Transmission; (RH engine compartment)
G5 07-10 Transmission; (LH strut tower)
G6 06-10 Transmission; (LH strut tower)
GRAND PRIX 06-08 Transmission; (lower air cleaner housing)
HHR 06-11 Transmission; (LH engine compartment)
HUMMER H3 08-10 Transmission; (RH rear engine compartment)
IMPALA 06-11 Transmission; (lower air cleaner housing)
ION 06-07 Transmission; (behind LH strut tower)
LACROSSE 06-09 Transmission; (lower air cleaner housing)
LUCERNE 06-07 Transmission; (4.6L), (LH engine compartment)
LUCERNE 08-11 Transmission; (LH engine compartment)
MALIBU 06-10 Transmission; (LH frame rail)
MONTE CARLO 06-07 Transmission; (lower air cleaner housing)
MONTANA 06-09 Transmission; (LH strut tower)
PURSUIT 06 Transmission; (LH strut tower)
RAINIER 06-07 Transmission
RENDEZVOUS 06-07 Transmission; (air cleaner box)
SAAB 9-7X 06-09 Transmission; (LH engine compartment)
SAVANA 1500 VAN 06-14 Transmission; (RH engine compartment)
SAVANA 2500 VAN 06-14 Transmission; (RH engine compartment)
SAVANA 3500 VAN 06-14 Transmission; (RH engine compartment)
SIERRA 1500 PICKUP 07 Transmission; (new style, smooth door skin), (next to battery)
SIERRA 1500 PICKUP 08 Transmission; (next to battery)
SIERRA 1500 PICKUP 09-13 Transmission; (next to battery), w/o hybrid option
SIERRA 2500 PICKUP 07 Transmission; new style (smooth door skin), 6.0L, (next to battery)
SILVERADO 1500 PICKUP 07 Transmission; (new style, smooth door skin), (next to battery)
SILVERADO 1500 PICKUP 08 Transmission; (next to battery)
SILVERADO 1500 PICKUP 09-13 Transmission; (next to battery), w/o hybrid option
SILVERADO 2500 PICKUP 07 Transmission; new style (smooth door skin), 6.0L, (next to battery)
SSR 05-06 Transmission; (front LH frame)
SUBURBAN 1500 07-08 Transmission; (next to battery)
TAHOE 07 Transmission; (next to battery)
TAHOE 08-09 Transmission; (next to battery), w/o auxiliary oil cooler pump
TERRAZA 06-07 Transmission; (LH strut tower)
TRAILBLAZER 06-07 Transmission; (LH engine compartment), (8 cylinder)
TRAILBLAZER 08-09 Transmission; (LH engine compartment)
UPLANDER 06-09 Transmission; (LH strut tower)
VUE 07-08 Transmission; 2.4L, (LH front engine compartment)
VUE 09 Transmission; 2.4L, w/hybrid, LH side front engine compartment, (shift control)
VUE 09 Transmission; 2.4L, w/o hybrid; (LH front engine compartment)
VUE 10 Transmission
YUKON 07 Transmission; (next to battery)
YUKON 08 Transmission; (next to battery), w/o auxiliary oil cooler control
YUKON 09 Transmission; (next to battery), w/o auxiliary oil cooler pump
YUKON XL 1500 07-08 Transmission; (next to battery)
Frequently Asked Questions About This 2006 Trailblazer EXT TCM
What does ‘VIN Programmed’ actually mean for me?
What does ‘VIN Programmed’ actually mean for me?
It means we load your vehicle’s specific Vehicle Identification Number (VIN) and the latest GM software onto the module before we ship it. This ensures it communicates perfectly with your engine computer and other systems right out of the box, eliminating the need for an expensive programming session at a dealership.
Do I need to send my old TCM back? Is there a core charge?
No, there is absolutely no core charge for this part. You can keep your old module or dispose of it yourself, saving you the time and hassle of a return shipment.
Is this a difficult part for a DIYer to install?
Not at all. This is one of the more straightforward electronic component replacements. If you can disconnect a battery and use a basic wrench or socket set, you have all the skills needed. The entire process typically takes less than 30 minutes.
What if I install this module and still have shifting problems?
While this TCM is the most common cause for the symptoms listed, transmission issues can sometimes be mechanical (like a faulty solenoid or worn clutch packs). However, replacing the TCM is the most logical and cost-effective first step in the diagnostic process, especially if you have electronic fault codes. Our module comes with a one-year warranty for your peace of mind.