If you’re dealing with the all-too-common shifting headaches in your 2006-2011 Chevrolet HHR, you’ve come to the right place. As a technician with over two decades of experience, I’ve seen firsthand how a failing Transmission Control Module (TCM) can turn a reliable vehicle into a source of daily frustration. Hard slams into gear, getting stuck in limp mode, or a persistent check engine light are not just annoying—they’re signs that the brain of your transmission is failing. This VIN-programmed T42 TCM, part number 24238856, is the definitive, dealership-free solution to restore your HHR’s performance and your peace of mind.
Is Your HHR Showing These Telltale Signs?
- ✔ Abrupt, harsh, or erratic gear shifts that make driving uncomfortable.
- ✔ The vehicle is stuck in a single gear (often 2nd or 3rd), a condition known as “limp mode.”
- ✔ Check Engine Light or Transmission Warning Light is on, with Diagnostic Trouble Codes (DTCs) like P0700, P0750, or other solenoid-related faults.
- ✔ A noticeable delay when shifting from Park to Drive or Reverse.
- ✔ Failure to upshift or downshift correctly, leading to poor acceleration and terrible fuel economy.
- ✔ Intermittent loss of communication with the TCM, causing unpredictable behavior.
Case Study: A Tricky Diagnosis
A customer brought in their 2009 HHR with a classic complaint: ‘It drives fine for 10 minutes, then it starts banging into gear at stoplights.’ They had already replaced two shift solenoids with no luck. A quick scan showed a P0700 (Transmission Control System Malfunction) and an intermittent solenoid circuit code. Instead of throwing more parts at it, we looked at the root cause. In these GM vehicles, the T42 TCM is notorious for internal solder joint failures caused by heat cycles. We installed one of our pre-programmed modules, and the problem was solved in under an hour. It wasn’t the solenoids; it was the module controlling them all along.
The Definitive Solution: A Pre-Programmed 2006-2011 HHR TCM
The biggest hurdle in replacing a TCM has always been the expensive and time-consuming programming required at a dealership. We eliminate that step entirely. By providing us with your vehicle’s VIN during checkout, we can flash the module with the latest GM software specific to your HHR. This ensures it works perfectly right out of the box. It’s a true plug-and-play repair that restores communication, optimizes shift strategy, and clears those persistent fault codes for good.
Your Straightforward 30-Minute Installation Guide
- ✔ Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and help reset the system.
- ✔ Locate the Module: On the 2006-2011 HHR, the TCM is conveniently located in the left-hand (driver’s side) of the engine compartment. It’s a silver box with electrical connectors.
- ✔ Disconnect and Remove: Carefully unclip the electrical wiring harnesses. Then, unbolt the old module from its mounting bracket. Typically, this only requires a basic socket set.
- ✔ Install the New TCM: Mount your new, pre-programmed module in the same location and securely fasten the bolts. Reconnect the wiring harnesses—they will only fit one way.
- ✔ Final Steps: Reconnect the battery terminal. While our programming handles the critical setup, it’s always good practice to use a basic OBD2 scanner to clear any stored fault codes from the vehicle’s memory.
Verified Vehicle Compatibility
This module is a direct-fit replacement for the 2006-2011 Chevrolet HHR. It is also compatible with a wide range of other GM vehicles that use the T42 TCM, including the Chevrolet Cobalt, Pontiac G6, Saturn Ion, and more. It is an interchangeable replacement for part numbers 24252114, 24234503, 24235754, 24238856, and others listed in the full fitment data.
Frequently Asked Questions
Do I absolutely need to provide my VIN?
Yes. Providing your Vehicle Identification Number (VIN) is essential. This allows us to program the module with the exact software and calibrations for your HHR’s specific configuration, ensuring seamless plug-and-play installation and proper transmission function.
Will this fix my transmission if it’s slipping?
This module corrects electronic issues like harsh shifting, communication errors, and incorrect solenoid commands. If your transmission is mechanically worn out (e.g., burnt clutches causing slipping), a new TCM will not fix that. This part resolves the electronic faults that are extremely common on these vehicles.
Is any special learning procedure required after installation?
No. Our VIN programming handles the setup. After installation and clearing any old codes, the vehicle is ready to be driven. The system will perform any minor adaptations on its own during the first few drive cycles.
What if I have a different part number on my old module?
GM uses many different service numbers for the same part over its production life. This module, part number 24238856, is a common service replacement for many others. Check our full interchange list or contact us with your original part number to confirm compatibility.
Is there a core charge?
No, there is no core charge for this module. You can keep your old part without the hassle or expense of sending it back.