Restore Smooth Shifting to Your GMC Envoy
If your 2006-2009 GMC Envoy is suffering from erratic shifting, getting stuck in gear, or throwing transmission codes, the culprit is often a failing Transmission Control Module (TCM). As the electronic brain of your automatic transmission, a faulty TCM can make your reliable SUV feel unpredictable and unsafe. I’ve seen countless GM vehicles in my shop with these exact issues, and a quality replacement module is the definitive solution. This T42 TCM, part number 24238856, is the answer to those frustrating transmission woes.
This isn’t just a replacement part; it’s a complete, hassle-free solution. We pre-program each module to your vehicle’s specific VIN, loading the latest GM software updates. This means it arrives ready for a true plug-and-play installation, eliminating the need for an expensive trip to the dealership for programming. For the professional mechanic, this means faster turnaround times in the bay. For the DIY enthusiast, it means you can confidently complete the job in your own driveway.
Case Study: A Tricky Diagnosis
A customer brought in a 2008 Envoy that would intermittently refuse to shift out of 2nd gear, especially after it warmed up. The check engine light was on, and his scanner pulled a generic P0700 (Transmission Control System Malfunction) and a specific solenoid code. He had already replaced the indicated shift solenoid, but the problem persisted. After a quick data stream check, I saw erratic commands from the TCM. The internal circuitry was failing under heat, a classic symptom I’ve diagnosed on over 100 T42 modules. We installed a VIN-programmed module, cleared the codes, and the Envoy was shifting like new in under an hour. This highlights how a failing TCM can mimic other component failures, making a reliable module the key to an accurate repair.
Is Your Envoy Exhibiting These Telltale Signs?
A failing TCM will give you clear warnings. If you’re experiencing any of the following, it’s time to consider a replacement 2006-2009 Envoy TCM.
- ✔ Harsh, slamming shifts or sudden, jerky gear changes.
- ✔ The vehicle feels stuck in one gear (often called ‘limp mode’).
- ✔ Significant delay when shifting from Park to Drive or Reverse.
- ✔ Illuminated Check Engine or Transmission warning lights on the dash.
- ✔ Diagnostic Trouble Codes (DTCs) such as P0700, P0750, P0753, P0758, or other solenoid-related faults.
- ✔ Poor fuel economy and a feeling of lost power.
- ✔ Complete failure to shift gears.
Your Step-by-Step Installation Guide
Installing your new transmission module is a straightforward process that most DIYers can handle in about 30 minutes with basic hand tools. For the 2006-2009 GMC Envoy, the TCM is typically located in the left-hand (driver’s side) of the engine compartment.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the vehicle’s computer systems.
- Locate the Module: Find the TCM on the driver’s side of the engine bay. It’s a silver box with electrical connectors.
- Disconnect and Remove: Carefully unplug the electrical harnesses from the old module. Then, unbolt the module from its mounting bracket.
- Install the New Module: Mount your new, pre-programmed TCM onto the bracket and securely plug in the electrical connectors. You should hear a ‘click’ as they lock into place.
- Reconnect and Verify: Reconnect the negative battery terminal. Start the vehicle and ensure all warning lights are off. It’s a good practice to use a basic OBD2 scan tool to confirm no codes are present.
Verified Fitment for Your Vehicle
While this is the primary replacement 2006-2009 Envoy TCM, this versatile T42 module is also a direct-fit, VIN-programmed solution for a wide range of other General Motors vehicles. It is interchangeable with part numbers 24252114, 24234503, 24238856, and more. Please verify your vehicle is on the list below for guaranteed compatibility.
- GMC Envoy / Envoy XL / Trailblazer / Trailblazer EXT: 2006-2009 (LH engine compartment)
- Chevrolet Silverado / GMC Sierra 1500, 2500: 2007-2013 (Located next to battery)
- Chevrolet Tahoe / Suburban / GMC Yukon: 2007-2009 (Located next to battery)
- Chevrolet Express / GMC Savana Vans: 2006-2014 (RH engine compartment)
- Chevrolet Impala / Monte Carlo: 2006-2011 (Lower air cleaner housing)
- Buick LaCrosse / Allure / Lucerne: 2006-2011 (Varies by model)
- Cadillac DTS: 2006-2011 (RH front engine compartment)
- Pontiac G6 / Grand Prix: 2006-2010 (LH strut tower)
- …and many other GM models from 2006-2014.
Frequently Asked Questions
Do I need to get this module programmed by a dealer?
No. We pre-program the module to your vehicle’s VIN before shipping. It arrives ready for installation, saving you time and money by avoiding a trip to the dealership.
Is this a difficult part to install myself?
Not at all. For most vehicles, including the GMC Envoy, it’s a simple plug-and-play process that takes less than 30 minutes with basic tools. Just locate the old module, swap it with the new one, and reconnect the battery.
What is a core charge?
A core charge is a deposit you pay until you return your old part. We do not require a core charge for this module, so you can keep your old part without any hassle or extra steps.
Will this fix a P0700 check engine light code?
Yes, in many cases. The P0700 code is a general fault code indicating the TCM has detected a problem. If the TCM itself is the source of the failure, replacing it with our programmed module will resolve the issue and allow the code to be cleared.
What kind of warranty is included?
This module is backed by our one-year warranty, giving you peace of mind and confidence in your repair.