If your 2006-2009 Chevrolet Trailblazer is suffering from erratic shifting, getting stuck in gear, or throwing transmission codes, you’ve likely pinpointed the culprit: a failing Transmission Control Module (TCM). As a seasoned technician, I’ve seen countless GM vehicles, especially the Trailblazer, come into the shop with these exact issues. The T42 TCM is the brain of your automatic transmission, and when it fails, it can make your reliable SUV feel unpredictable and unsafe. This isn’t just a part; it’s the solution to restore your vehicle’s drivability and your peace of mind.
This replacement TCM, part number 24241806, is the definitive fix for these common ailments. We take the biggest hassle out of the repair by pre-programming the module to your vehicle’s specific VIN. This means you can skip the expensive trip to the dealership for programming. It arrives at your door ready for a true plug-and-play installation, loaded with the latest GM software updates to ensure optimal communication between your engine and transmission.
Case Study: A Tricky Diagnosis
A customer brought in a 2008 Trailblazer with a complaint that was driving him crazy: intermittent, bone-jarring shifts from 1st to 2nd gear, but only after it was fully warmed up. No consistent check engine light, just an occasional P0700 code that would clear itself. We checked the fluid, inspected the solenoids, and couldn’t find a mechanical fault. Experience pointed to an electronic gremlin. We swapped in a pre-programmed T42 TCM, and the problem vanished instantly. The original module’s internal circuits were failing under heat, a classic failure I’ve diagnosed on hundreds of these GM platforms. This part saved the customer from a potential transmission rebuild.
Is Your Trailblazer Showing These Symptoms?
A faulty TCM can manifest in several ways. If you’re noticing any of the following, it’s a strong indicator that your 2006-2009 Trailblazer TCM needs replacement:
- âś” Harsh, delayed, or slamming gear shifts.
- âś” The vehicle is stuck in “limp mode” (usually 2nd or 3rd gear).
- âś” Check Engine Light or Transmission Warning Light is on with DTCs like P0700, P0750, P0753, P0758, or other solenoid-related codes.
- âś” Inability to upshift or downshift properly.
- âś” A sudden drop in fuel economy.
- âś” The torque converter failing to lock up, causing poor highway performance.
Your 30-Minute Path to a Smooth Ride
One of the best parts about this solution is how simple it is for a DIYer or a professional mechanic. No special tools are needed, and you can have your Trailblazer running smoothly in under half an hour.
- Safety First: Always disconnect the negative terminal on your vehicle’s battery before starting any electronic repair.
- Locate the Module: On the 2006-2009 Trailblazer, the TCM is typically found in the engine compartment on the left-hand (driver’s) side.
- Perform the Swap: Carefully disconnect the wiring harnesses from the old TCM. Unbolt the module from its mounting bracket. Install the new, pre-programmed module in its place, re-secure the bolts, and firmly reconnect the harnesses.
- Final Steps: Reconnect the battery terminal. While the module is plug-and-play, it’s best practice to use a basic OBD2 scan tool to clear any stored diagnostic trouble codes from the vehicle’s memory.
Verified Vehicle Compatibility
This T42 TCM is a direct replacement for part number 24241806 and is interchangeable with many other service numbers. While it fits a wide range of GM vehicles, it has been confirmed for the following:
- TRAILBLAZER 2006-2007 (Transmission; LH engine compartment, 8 cylinder)
- TRAILBLAZER 2008-2009 (Transmission; LH engine compartment)
- TRAILBLAZER EXT 2006 (Transmission; LH engine compartment, 8 cylinder)
- And many other GM models including the Envoy, Rainier, Saab 9-7X, Silverado, Tahoe, Sierra, Yukon, and more as listed in the full compatibility chart.
- Frequently Asked Questions (FAQ)
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What exactly does a Transmission Control Module do?
The TCM is a computer that acts as the ‘brain’ for your automatic transmission. It receives data from various sensors on the engine and vehicle, and uses that information to control when to shift gears, how firmly to shift, and when to engage the torque converter clutch for maximum efficiency.
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Is this part really ‘plug-and-play’?
Yes. The main reason a new TCM requires a dealer visit is for programming. We perform this critical step for you by flashing the module with your vehicle’s VIN and the latest GM software before we ship it. This ensures it communicates correctly with your vehicle right out of the box.
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Where is the TCM located on my 2007 Trailblazer?
For the 2006-2009 Chevrolet Trailblazer, the Transmission Control Module is located in the engine bay, on the driver’s side (LH) of the engine compartment.
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Do I need to send my old TCM back?
No. There is no core charge or requirement to return your old, faulty part. You can dispose of it at your convenience.
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I installed the new module, but my check engine light is still on. What’s next?
After installation, any old fault codes will remain stored in the main computer’s memory. You will need to use a standard OBD2 scan tool to clear these stored codes. Once cleared, they should not return.