Fix Your GMC Envoy’s Shifting Problems for Good
If your 2006-2009 GMC Envoy is suffering from harsh shifts, delayed gear engagement, or is stuck in limp mode, you’ve likely pinpointed the problem: a failing Transmission Control Module (TCM). Over my 20+ years in automotive diagnostics, I’ve seen hundreds of these T42 TCMs fail, causing immense frustration for drivers. This isn’t just an inconvenience; it’s a critical component failure that impacts your SUV’s performance and safety. This replacement 2006-2009 Envoy TCM is the definitive solution, arriving pre-programmed to your vehicle’s VIN for a hassle-free, plug-and-play installation.
Case Study: A Tricky Diagnosis
A few months back, a 2007 Envoy with the 8-cylinder engine came into my bay. The owner was told he needed a complete transmission rebuild due to severe gear slamming and a persistent Check Engine light with a P0700 (Transmission Control System Malfunction) code. Before tearing anything apart, I did a full diagnostic. The transmission fluid was clean, and the solenoids tested within spec. The real issue was internal to the TCM—its processors were failing under heat, causing erratic signals. We installed a VIN-programmed module like this one, and the vehicle was shifting like new in under an hour, saving the customer thousands of dollars and a week of downtime.
Is Your Envoy Exhibiting These Transmission Issues?
A faulty TCM can manifest in several ways. If you’re experiencing any of the following, this module is the likely solution your vehicle needs.
- ✔ Harsh, erratic, or delayed shifting between gears.
- ✔ Vehicle is stuck in a single gear (often called “limp mode”).
- ✔ Check Engine Light or Transmission Warning Light is illuminated.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750, or other solenoid-related faults.
- ✔ Complete loss of upshifting or downshifting capabilities.
- ✔ Decreased fuel efficiency and potential for transmission overheating.
A Straightforward Guide to Your Envoy’s TCM Replacement
One of the best features of this part is its simple installation. You don’t need to be a professional mechanic to get this done in your own driveway. For the 2006-2009 Envoy, the process is very accessible.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electronic component replacement.
- Locate the Module: On your GMC Envoy, the TCM is typically found in the engine compartment on the driver’s side (LH).
- Swap the Part: Carefully disconnect the electrical connectors from the old module. Unbolt it from its mounting bracket and remove it. Install the new module in its place, securing the bolts and reconnecting the wiring harnesses firmly.
- Reconnect and Verify: Reconnect the battery terminal. Start the vehicle and let it idle for a moment. The new, VIN-programmed module will immediately communicate with your vehicle’s other systems.
- Clear the Codes: While disconnecting the battery may clear codes, it’s best practice to use a basic OBD2 scan tool to clear any stored transmission fault codes to ensure a clean slate for the new module.
Verified Fitment for Your GM Vehicle
This T42 Transmission Control Module, part number YNXS, is a direct replacement for a wide range of General Motors vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. While this page focuses on the 2006-2009 Envoy TCM, it is also compatible with many other models. It interchanges with part numbers 24252114, 24234503, 24230461, and more. Please see the detailed list below to confirm your specific vehicle.
Frequently Asked Questions
What is a TCM and what does it do?
The Transmission Control Module (TCM) is a computer that acts as the brain for your automatic transmission. It receives data from engine and wheel speed sensors to control shift points, torque converter lockup, and line pressure, ensuring smooth and efficient operation.
Why is VIN programming so important?
VIN programming loads your vehicle’s specific software and calibrations onto the module before it ships. This makes it truly plug-and-play, eliminating the need for an expensive trip to the dealership for programming. It ensures perfect communication and performance right out of the box.
Will this fix my P0700 code?
A P0700 code is a general fault code indicating the TCM has detected a problem. In many cases, a failing TCM is the root cause, and replacing it will resolve the P0700 and any related specific codes (like for solenoids). However, always ensure the wiring and connectors are in good condition first.
Is this part difficult to install myself?
No, for most DIYers with basic hand tools, this is a very manageable job. On the Envoy, the module is easily accessible in the engine bay. The entire process typically takes less than 30 minutes.
Do I need to send my old part back?
No, there is no core charge for this part. You can keep or dispose of your old module without any hassle or additional cost.