If you’re dealing with the frustration of a Chevrolet HHR that bangs into gear, refuses to shift, or is stuck in limp mode, you’ve likely pinpointed the culprit: a failing Transmission Control Module (TCM). As a technician with over two decades of experience, I’ve seen countless GM vehicles, especially the HHR, sidelined by these exact issues. This isn’t just an inconvenience; it’s a safety concern. This T42 series TCM, part number 24238856, is the definitive, reliable solution to restore your vehicle’s drivability and your peace of mind.
The core of the problem often lies in the original module’s vulnerability to heat and vibration, leading to internal circuit failures. This replacement 2006-2011 HHR TCM is built to meet and exceed original equipment standards, ensuring a durable and long-lasting repair. The most significant benefit we offer is the pre-programming. We flash the module to your specific Vehicle Identification Number (VIN) before it ships, eliminating the need for expensive dealership visits and specialized scan tools. It arrives at your door ready for a true plug-and-play installation.
Case Study: The HHR That Wouldn’t Shift
A customer brought in their 2009 HHR with a classic complaint: it would drive fine for a few minutes, then the transmission warning light would pop on, and it would get stuck in what felt like 2nd or 3rd gear. They had already replaced a shift solenoid based on a P0753 code, but the problem persisted. After a quick check of the wiring harness, my diagnostic process led me straight to the TCM. Heat soak was causing an intermittent open circuit inside the module. We installed one of our VIN-programmed TCMs, and the problem was solved instantly. The customer saved hundreds by avoiding further guesswork and dealership programming fees. This is a story I’ve seen play out time and time again with these vehicles.
Is Your HHR Transmission Showing These Warning Signs?
A faulty TCM can manifest in several ways. If you’re experiencing any of the following, it’s a strong indicator that your module needs replacement:
- ✔ Harsh, delayed, or erratic gear shifts that make driving uncomfortable.
- ✔ The vehicle is stuck in “limp mode,” refusing to shift out of a single gear.
- ✔ Check Engine Light or Transmission Warning Light is illuminated on the dash.
- ✔ Diagnostic Trouble Codes (DTCs) are present, such as P0700 (Transmission Control System Malfunction), or specific solenoid codes (e.g., P0751, P0756).
- ✔ A noticeable decrease in fuel economy due to inefficient shifting.
- ✔ Complete loss of communication with the TCM, preventing diagnostics.
Your Step-by-Step HHR TCM Installation Guide
Replacing the 2006-2011 HHR TCM is a straightforward job that most DIY mechanics can complete in under 30 minutes with basic hand tools. For the 2006-2011 HHR, the TCM is conveniently located in the left-hand (driver’s side) engine compartment.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery to prevent electrical shorts and reset the system.
- Locate the TCM: Open the hood and find the module on the driver’s side of the engine bay. It’s a silver box with electrical connectors.
- Disconnect and Remove: Carefully unplug the electrical connectors. Note the locking tabs to avoid damage. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, VIN-programmed TCM into place. Securely reconnect the electrical harnesses until they click.
- Final Steps: Reconnect the battery terminal. Start the vehicle and allow it to idle for a few minutes. While our programming handles the critical setup, it’s good practice to use a basic scan tool to clear any stored fault codes from the ECU.
Verified Vehicle Compatibility
This module is a direct replacement for part number 24238856 and other interchangeable numbers. While it is guaranteed to fit the 2006-2011 HHR TCM application, it also fits a wide range of other GM vehicles. Please confirm your part number or contact us with your VIN to ensure perfect fitment.
Do I need to have this module programmed by a dealer?
Do I need to have this module programmed by a dealer?
No. The main benefit of our service is that we program the module to your vehicle’s VIN before shipping. This makes the installation plug-and-play, with no additional programming or dealer visits required.
Is there a core charge for my old part?
No, we do not require a core return. You can keep your old part, which saves you the time, money, and hassle of shipping it back.
What tools are needed for installation on an HHR?
Installation typically only requires basic hand tools, such as a socket set and a ratchet to unbolt the module and disconnect the battery. No specialized equipment is necessary.
Will this fix a P0700 trouble code?
A P0700 code is a general fault request from the TCM to the Engine Control Module (ECM) to turn on the Check Engine Light. In the vast majority of cases where the TCM itself has failed, replacing it with this programmed unit will resolve the P0700 code and any related transmission-specific codes.