Fix Your Monte Carlo’s Shifting Problems for Good
Is your 2006-2007 Chevrolet Monte Carlo shifting erratically, getting stuck in gear, or throwing transmission codes? You’re not alone. After 20 years in the garage, I’ve seen countless GM vehicles with these exact issues, and the culprit is almost always a failing Transmission Control Module (TCM). A faulty TCM can make your car feel unpredictable and unsafe. This T42 TCM, part number YNXS, is the definitive, hassle-free solution. It arrives expertly programmed to your car’s specific VIN, making it a true plug-and-play fix that restores the crisp, smooth shifting you expect from your Monte Carlo.
Case Study: The Ghost in the Transmission
A Technician’s Notebook
A customer brought in his ’07 Monte Carlo with a frustrating problem: intermittent harsh shifting and occasionally getting stuck in 3rd gear (limp mode). He’d already replaced a shift solenoid with no luck. On the scan tool, we saw a generic P0700 code, but the real issue was intermittent communication loss with the TCM. These T42 modules are known to develop internal circuit faults from heat and vibration over time. Instead of a costly diagnostic rabbit hole, we installed one of our pre-programmed modules. The entire job took less than 30 minutes, and the car shifted perfectly on the test drive. The customer saved hundreds compared to a dealership visit and got his car back the same day. This module is the fix I trust in my own bay.
Diagnosing a Faulty 2006-2007 Monte Carlo TCM
The Transmission Control Module is the brain of your automatic transmission, controlling everything from shift points to torque converter lockup. When it fails, the symptoms are often obvious and disruptive. If you’re experiencing any of the following, a failing TCM is the likely cause.
Common Signs of a Failing T42 TCM
- ✔ Harsh, slamming shifts or delayed gear engagement.
- ✔ Vehicle is stuck in a single gear (often called “limp mode”).
- ✔ Check Engine Light or Transmission Warning Light is on.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750, or other solenoid-related faults.
- ✔ Inconsistent or no upshifting/downshifting.
- ✔ A noticeable drop in fuel economy.
- ✔ The transmission feels like it’s slipping between gears.
A Straightforward Guide to Installation
One of the biggest benefits of this module is its simple, DIY-friendly installation. Because it comes pre-programmed, you avoid a trip to the dealer. For the 2006-2007 Monte Carlo, the TCM is located under the lower air cleaner housing, making it accessible with basic hand tools.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and help reset the system.
- Locate the Module: On your Monte Carlo, you’ll need to access the area beneath the air cleaner box to find the old TCM.
- Disconnect and Remove: Carefully unplug the electrical connectors from the old module. Then, unbolt it from its mounting bracket.
- Install the New TCM: Bolt the new, pre-programmed module into place and securely reconnect the electrical harnesses. Ensure they click into place.
- Final Steps: Reconnect the battery terminal. While the system may reset on its own, it’s best practice to use a basic OBD2 scanner to clear any stored transmission codes. Start the car and enjoy smooth shifting!
Verified Vehicle Compatibility
This T42 TCM is a direct replacement for part number YNXS and is interchangeable with a wide range of other service numbers, including 24252114, 24234503, 24230461, and more. While this page focuses on the 2006-2007 Monte Carlo TCM, it also fits many other GM vehicles. Please verify your specific model in the list below:
Fits Chevrolet: Monte Carlo (06-07), Impala (06-11), Silverado, Tahoe, Cobalt, HHR, and more.
Fits GMC: Sierra, Yukon, Savana, Canyon, Envoy.
Fits Buick: LaCrosse (06-09), Lucerne (06-11), Allure, Rendezvous.
Fits Pontiac: G6 (06-10), Grand Prix (06-08), G5, Pursuit.
…and many other Cadillac, Saturn, Hummer, and Saab models from the era.
Frequently Asked Questions
Do I need to do any programming myself?
No. This module comes 100% pre-programmed to your vehicle’s VIN. It is ready for installation right out of the box, with no need for a scan tool or a trip to the dealership for programming.
Is there a core charge for my old part?
Absolutely not. We do not require you to send back your old, faulty module. You can keep it or dispose of it at your convenience, saving you time and return shipping costs.
What tools do I need for the installation?
For a 2006-2007 Monte Carlo, the installation typically requires only basic hand tools, such as a socket set and a screwdriver, to access and remove the air cleaner housing and the module itself.
Will this fix a P0700 trouble code?
A P0700 code is a general transmission fault request, meaning another, more specific code is stored. Often, the underlying cause is a faulty TCM. Replacing a confirmed-bad TCM will resolve the issue and allow you to clear the P0700 code permanently.
Where is the TCM located on my 2007 Monte Carlo?
On the 2006-2007 Chevrolet Monte Carlo, the Transmission Control Module (TCM) is located under the lower air cleaner housing in the engine bay.