If your 2006 Chevrolet Trailblazer EXT is suffering from delayed shifts, getting stuck in gear, or throwing transmission codes, you’re likely dealing with 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 reliable SUV. This isn’t just an annoyance; it’s a critical failure that impacts drivability and safety. This T42 TCM, part number 24235753, is the definitive solution, arriving pre-programmed to your vehicle’s specific VIN for a true plug-and-play repair.
From the Diagnostic Bay: A Trailblazer’s Tale
A customer brought in their ’06 Trailblazer EXT, complaining it was stuck in 3rd gear (limp mode) and the check engine light was on. They’d already replaced a shift solenoid on a friend’s advice, but the problem persisted. A quick scan showed a P0700 (Transmission Control System Malfunction). Instead of just chasing solenoid codes, we checked the TCM communication. We found intermittent data loss, a classic sign of internal TCM failure. After installing one of our VIN-programmed modules, all codes cleared, and the transmission shifted like new. It’s a common story: the TCM is the brain, and when it fails, the whole system gets confused.
Common Signs of a Failing GM T42 TCM
A bad TCM can manifest in several ways. If you’re experiencing any of these issues, it’s a strong indicator that your module needs replacement. Don’t let these problems lead to more expensive transmission damage.
- ✔ Unpredictable, harsh, or jerky gear shifts.
- ✔ The vehicle refuses to shift out of a certain gear, often referred to as “limp mode.”
- ✔ Illumination of the Check Engine Light, often with Diagnostic Trouble Codes (DTCs) like P0700, P0750, P0753, P0758, or other solenoid-related faults.
- ✔ Failure to upshift or downshift, leading to poor acceleration and terrible fuel economy.
- ✔ Complete loss of communication with the TCM, preventing diagnostics.
- ✔ Delayed engagement when shifting from Park to Drive or Reverse.
DIY-Friendly Installation Guide
Replacing the 2006 Trailblazer EXT TCM is a job most DIYers can handle in their own garage in under 30 minutes. No specialized tools are required.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- Locate the Module: On the 2006 Trailblazer EXT, the TCM is typically found in the left-hand (driver’s side) engine compartment.
- Disconnect and Remove: Carefully unclip the wiring harness connectors. Be gentle to avoid damaging the pins or clips. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, pre-programmed TCM into place. Reconnect the wiring harnesses, ensuring they click securely into position.
- Final Steps: Reconnect the battery terminal. While our VIN programming handles the critical setup, it’s good practice to use a basic OBD2 scan tool to clear any stored fault codes from the vehicle’s memory.
Verified Vehicle Compatibility
This module is a direct-fit replacement for a wide range of General Motors vehicles equipped with 4-speed automatic transmissions like the 4L60E and 4L65E. While this page focuses on the 2006 Trailblazer EXT TCM, it is also compatible with the following models. Please verify your part number (24235753 or an interchange number) for a guaranteed fit.
- Chevrolet: Silverado, Tahoe, Suburban, Avalanche, Express, Colorado, Impala, Cobalt, HHR, Monte Carlo, SSR
- GMC: Sierra, Yukon, Savana, Canyon, Envoy / Envoy XL
- Buick: Rainier, LaCrosse, Lucerne, Allure, Rendezvous
- Cadillac: DTS
- Pontiac: G5, G6, Grand Prix, Pursuit
- Saturn: Vue, Ion, Aura
- Hummer: H3
- Saab: 9-7X
This part is interchangeable with the following service numbers: 24242391, 24234503, 24252114, 24230461, 24234274, 24235340, 24235754, 24238856, 24239224, 24239926, 24240400, 24241806, 24243901, 24243921, 24255280, 24256960, 24235732, 24240449, YNXS.
Do I need to take this part to the dealer for programming?
Do I need to take this part to the dealer for programming?
No. This module comes fully programmed to your vehicle’s VIN. It is ready for installation right out of the box, saving you the time and expense of a dealership visit.
Is there a core charge for my old TCM?
No, there is no core charge. You can keep your old part or dispose of it without the hassle of returning it.
What causes a TCM to fail?
TCM failures are often caused by heat cycles, vibration, and age. Over time, solder joints on the circuit board can crack, or electronic components can fail, leading to the symptoms described.
Will this fix a P0700 code on my Trailblazer?
A P0700 is a generic code indicating the TCM has detected a fault. While a failing 2006 Trailblazer EXT TCM is a very common cause, you should always scan for other transmission-specific codes (e.g., P07xx) to confirm the diagnosis. In many cases, replacing the TCM will resolve the root cause of the P0700 code.