If your 2006-2009 Chevrolet Trailblazer is suffering from erratic shifting, getting stuck in gear, or throwing transmission-related check engine lights, you’ve likely pinpointed the culprit: a failing Transmission Control Module (TCM). As a technician with over two decades of experience, I’ve seen firsthand how a faulty TCM can sideline an otherwise perfectly good vehicle. This isn’t just an annoyance; it’s a critical failure that compromises drivability and safety. This T42 TCM, service part number 24238856, is the definitive, hassle-free solution to restore your transmission’s performance.
The biggest hurdle in replacing a modern electronic module is programming. Dealerships charge a premium for this service, adding time and cost to your repair. We eliminate that step entirely. By providing your vehicle’s VIN at checkout, we program the module with the latest GM software updates specific to your Trailblazer. It arrives at your door ready for a true plug-and-play installation, getting you back on the road faster and saving you money.
A Technician’s Notebook: The Trailblazer Stuck in Limp Mode
A customer brought in a 2008 Trailblazer with the 5.3L V8. The complaint was simple: the check engine light was on, and it felt like the truck was ‘stuck’ in one gear. It was sluggish from a stop and wouldn’t shift up on the highway. My scan tool pulled a P0700 (Transmission Control System Malfunction) and several solenoid-specific codes. After verifying the wiring and solenoid resistances were within spec, all signs pointed to the TCM. The internal logic had failed, causing it to command limp mode to protect the transmission. We installed one of our pre-programmed T42 modules, and in less than an hour, the truck was shifting perfectly, with all codes cleared. This is a classic failure mode for the 2006-2009 Trailblazer TCM.
Is Your Trailblazer Exhibiting These Telltale Signs?
- ✔️ Harsh, slamming shifts or delayed gear engagement.
- ✔️ Vehicle is stuck in ‘limp mode,’ often in 2nd or 3rd gear.
- ✔️ The check engine light or transmission warning light is illuminated.
- ✔️ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750, P0753, P0758, or other solenoid-related faults.
- ✔️ Inconsistent shifting patterns or complete failure to shift up or down.
- ✔️ A noticeable drop in fuel economy or signs of the transmission overheating.
A Straightforward Guide to Installation
- ✔ Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the system.
- ✔ Locate the Module: On the 2006-2009 Trailblazer, the TCM is typically found in the engine compartment on the left-hand (driver’s) side.
- ✔ Disconnect and Remove: Carefully unplug the electrical connectors from the old module. Then, unbolt the module from its mounting bracket.
- ✔ Install the New Module: Mount your new, pre-programmed TCM in place and securely fasten the bolts. Reconnect the electrical harnesses, ensuring they click into place.
- ✔ Final Steps: Reconnect the battery terminal. Start the vehicle and use a basic scan tool to clear any stored diagnostic codes. Take the vehicle for a test drive to confirm smooth shifting.
Verified Vehicle Compatibility
This module is a direct replacement for part number 24238856 and other interchangeable numbers. While it is the correct part for the 2006-2009 Trailblazer, it also fits a wide range of other GM vehicles. Please verify your part number or consult the fitment list below.
Partial Fitment List:
- 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 06-09
- RAINIER 06-07
- SAAB 9-7X 06-09
- SILVERADO, SIERRA, TAHOE, YUKON, AVALANCHE (Various Years)
- IMPALA, MONTE CARLO, LACROSSE (Various Years)
- …and many more GM models from 2006-2014.
Frequently Asked Questions about the 2006-2009 Trailblazer TCM
Frequently Asked Questions
What does ‘VIN Programmed’ actually mean for me?
It means we load the module with the specific software and calibrations for your Trailblazer’s exact configuration (engine, transmission, options) using your Vehicle Identification Number. This makes the part work correctly right out of the box, saving you from a mandatory and costly programming session at a dealership.
Do I need any special tools for this installation?
No. The installation only requires basic hand tools, such as a socket set to remove the module’s mounting bolts. A code reader or scan tool is recommended to clear any old codes after the job is done, but it’s not required for the module to function.
Is there a core charge for this part?
No, there is no core charge. You are not required to send your old, faulty module back to us, which simplifies the process for you.
What happens if I keep driving with a bad TCM?
Continuing to drive with a faulty TCM can lead to more severe and expensive damage. Poor shifting can cause excessive wear on clutches and bands inside the transmission, potentially leading to a complete mechanical failure that requires a full transmission rebuild or replacement.
Does this part come with a warranty?
Yes, this transmission control module is backed by our one-year warranty, giving you peace of mind that you’re installing a quality, reliable part.