Restore Flawless Shifting to Your Chevrolet HHR
If you’re dealing with the frustration of a 2006-2011 Chevrolet HHR that bangs into gear, refuses to shift, or is stuck in limp mode, the problem often points directly to a failed Transmission Control Module (TCM). As the electronic brain of your automatic transmission, the T42 TCM is responsible for every shift command. Over years of heat cycles and vibration in the engine bay, these modules can develop internal faults, leading to a host of drivability issues that can make your HHR feel unreliable and unsafe.
I’ve seen this exact scenario play out hundreds of times in my 20 years as a technician. A customer comes in worried they need a costly transmission rebuild, but a quick scan reveals classic TCM failure codes. This module, part number 24243921, is the precise, dependable solution. It’s not just a replacement part; it’s a permanent fix that arrives pre-programmed to your vehicle’s specific VIN. This means you can skip the expensive trip to the dealership for programming—it’s ready for installation right out of the box, restoring the crisp, predictable shifting you expect.
Case Study: A Tricky Diagnosis
A customer brought in their 2009 HHR with an intermittent ‘Check Engine’ light and a complaint that it would occasionally get stuck in 3rd gear. They had already replaced two shift solenoids at another shop with no success. After connecting my scan tool, I saw a P0700 (Transmission Control System Malfunction) code, which is a general flag, but digging deeper, I found intermittent communication loss codes with the TCM. Instead of throwing more parts at it, we inspected the module. We installed this VIN-programmed TCM, and the problem was solved instantly. It saved the customer from a potential transmission replacement, reinforcing that proper diagnosis starts with the brain—the TCM.
Is Your HHR Showing These Telltale Signs?
A failing TCM will give you clear warnings. If you’re experiencing any of the following, it’s highly likely your module is the culprit. Replacing the 2006-2011 HHR Transmission Control Module is the most common and effective solution.
- ✔ Harsh, slamming shifts or delayed gear engagement.
- ✔ Vehicle is stuck in a single gear (often called “limp mode”).
- ✔ The check engine light or transmission warning light is illuminated.
- ✔ Diagnostic Trouble Codes (DTCs) like P0700, P0750, or other solenoid-related codes are present.
- ✔ A complete loss of communication with the transmission module.
- ✔ Poor fuel economy and a feeling of sluggish performance.
A Straightforward Guide to Installation
One of the best features of this part is its simple, DIY-friendly installation. You don’t need a vehicle lift or specialized tools, and the entire process can be completed in under 30 minutes in your own driveway.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and help reset the system.
- Locate the TCM: On the Chevy HHR, the Transmission Control Module is typically found in the engine compartment, mounted on the left-hand (driver’s side) of the engine compartment.
- Disconnect and Remove: Carefully unplug the electrical connectors from the old module. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, pre-programmed TCM into place and securely reconnect the electrical harnesses. You’ll hear a ‘click’ when they are properly seated.
- Final Steps: Reconnect the battery terminal. Start the vehicle and allow it to idle for a few minutes. If you have a basic scan tool, it’s good practice to clear any stored DTCs.
Verified Vehicle Compatibility
This T42 Transmission Control Module is a direct-fit replacement for a wide range of General Motors vehicles. While this page focuses on the 2006-2011 HHR Transmission Control Module, it is also compatible with the following models. Always verify your part number (24243921) or consult the fitment list.
- Chevrolet HHR: 2006, 2007, 2008, 2009, 2010, 2011 (LH engine compartment)
- Chevrolet Cobalt: 2006-2010 (LH strut tower)
- Chevrolet Impala: 2006-2011 (lower air cleaner housing)
- Pontiac G6: 2006-2010 (LH strut tower)
- Saturn Vue: 2007-2010 (LH front engine compartment)
- …and many other GM models listed in the general fitment data.
Frequently Asked Questions
Do I need to have this module programmed by a dealer?
No. We handle all the programming for you. Simply provide your vehicle’s VIN during checkout, and the module will arrive ready for plug-and-play installation.
Is a core charge required for my old part?
No, there is no core charge. You can keep your old module or recycle it locally without the hassle of shipping it back.
Where is the TCM located on my 2008 Chevy HHR?
On the 2006-2011 HHR, the TCM is located in the engine bay, on the driver’s side (LH) engine compartment area, making it very accessible for replacement.
What if this doesn’t fix my problem?
This module is designed to fix issues directly caused by a faulty TCM. If your problems persist, it may indicate a mechanical issue within the transmission itself or a wiring problem. Our part is backed by a one-year warranty against defects.
Will this clear my Check Engine Light?
Yes, if the light was on due to TCM-related fault codes (like P0700), this replacement part will resolve the root cause. After installation, any stored codes should be cleared with a scan tool or by disconnecting the battery.