Is your 2006-2009 Pontiac Montana struggling with its automatic transmission? If you’re dealing with abrupt shifts, a check engine light that won’t quit, or the vehicle refusing to shift gears properly, you’re likely facing a faulty Transmission Control Module (TCM). As a technician with over two decades of experience, I’ve seen firsthand how a failing TCM can make a reliable vehicle feel unpredictable and unsafe. This isn’t just an inconvenience; it’s a critical failure that impacts drivability and fuel economy.
This T42 Transmission Control Module, corresponding to part number YNXS, is the definitive solution. It’s not just a replacement part; it’s a complete fix that arrives at your door pre-programmed to your Montana’s specific Vehicle Identification Number (VIN). This crucial step ensures seamless integration with your vehicle’s computer systems, restoring the precise, smooth shifting logic designed by the manufacturer. You get an OEM-quality repair without the exorbitant cost and hassle of dealership programming.
Is Your Montana Showing These Telltale Signs?
- ✔ Harsh, slamming, or erratic gear shifts.
- ✔ The vehicle is stuck in “limp mode” (usually 2nd or 3rd gear).
- ✔ Check Engine Light or Transmission Warning Light is on with codes like P0700 (Transmission Control System Malfunction) or solenoid-specific codes (P0751, P0756, etc.).
- ✔ Delayed engagement when shifting from Park to Drive or Reverse.
- ✔ Complete failure to upshift or downshift.
- ✔ A noticeable decrease in fuel efficiency.
Case Study: A Tricky Diagnosis
A customer brought in their family’s 2008 Montana, convinced the transmission was shot. It was banging into gear and occasionally wouldn’t shift past 2nd. They were quoted nearly $3,000 for a transmission rebuild at another shop. After connecting my scan tool, I saw a classic P0756 (Shift Solenoid ‘B’ Performance/Stuck Off) code. While this can point to a solenoid, experience told me to check the source. We tested the TCM’s outputs and found intermittent signal loss—a common failure point in these T42 modules. Instead of a costly rebuild, we installed a VIN-programmed 2006-2009 Montana TCM. The total repair took less than an hour and saved the customer thousands. It’s a perfect example of why you should always diagnose the electronics before condemning the hard parts.
Quick and Easy Installation Guide
- ✔ Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent electrical shorts and reset the onboard systems.
- ✔ Locate the Module: On the Pontiac Montana and similar vans (Uplander, Terraza), the TCM is typically mounted on the driver’s side strut tower in the engine bay. It’s a silver box with electrical connectors.
- ✔ Disconnect and Remove: Carefully unplug the electrical harnesses. Then, unbolt the module from its mounting bracket. Keep the hardware safe.
- ✔ Install the New TCM: Mount the new module securely using the original hardware. Reconnect the electrical harnesses, ensuring they click firmly into place.
- ✔ Final Steps: Reconnect the battery terminal. While our VIN programming handles the critical setup, it’s always best practice to use a basic OBD2 scan tool to clear any stored fault codes from the system. Start the vehicle and test drive to confirm smooth operation.
Confirmed Vehicle Compatibility
This module is a direct replacement for part number YNXS and other interchangeable numbers. While it is guaranteed to fit the 2006-2009 Pontiac Montana, it is also compatible with a wide range of other GM vehicles that use the T42 TCM platform. Always verify your part number or consult our fitment list to ensure a perfect match. Common compatible models include:
- ✔ Pontiac Montana (2006-2009) – LH strut tower
- ✔ Chevrolet Uplander (2006-2009) – LH strut tower
- ✔ Buick Terraza (2006-2007) – LH strut tower
- ✔ Chevrolet Impala / Monte Carlo (2006-2011) – Lower air cleaner housing
- ✔ Pontiac G6 / Saturn Aura (2006-2010) – LH strut tower or frame rail
- ✔ Chevrolet HHR / Cobalt (2006-2011) – LH engine compartment/strut tower
- …and many other GM cars, trucks, and SUVs from 2006-2014.
Frequently Asked Questions
What does ‘VIN Programmed’ actually mean for me?
It means we load your vehicle’s unique 17-digit VIN into the module before shipping. This ensures it communicates perfectly with your Engine Control Module (ECM) and other systems, just like a part from the dealer, but without the extra cost or appointment for programming. It’s a true plug-and-play solution.
Do I need to send my old TCM back?
No, there is no core charge for this module. You can keep your old part, which saves you the time and expense of return shipping.
Will this 2006-2009 Montana TCM fix my P0700 code?
A P0700 code is a general fault code indicating the TCM has detected a problem and has requested the Check Engine Light be turned on. Often, a faulty TCM is the root cause. While this module resolves the issue in most cases, you should scan for other ‘P’ codes (like P07xx) to confirm the specific fault.
Is this a difficult part for a DIYer to install?
Not at all. For most vehicles like the Montana, the TCM is easily accessible in the engine bay. With basic hand tools and our guide, most people can complete the swap in under 30 minutes. The biggest benefit is that the complex programming part is already done for you.