Is Your Chevrolet HHR Running Rough? The PCM Might Be the Culprit.
The Powertrain Control Module (PCM), often called the Engine Control Module (ECM), is the central computer of your 2007-2011 Chevrolet HHR. It’s responsible for managing everything from fuel injection and ignition timing to transmission shifting and emissions control. When this critical component begins to fail, it can cause a cascade of confusing and frustrating problems that are often misdiagnosed, leading to wasted time and money on unnecessary parts.
This replacement PCM, compatible with service number 12635901 and others, is the definitive solution to restore your vehicle’s performance, reliability, and fuel efficiency. Unlike a generic part from a local store, this unit is professionally programmed specifically for your vehicle using your unique Vehicle Identification Number (VIN). This ensures seamless integration and operation, loaded with the latest software updates directly from GM.
From the Diagnostic Bay
We had a 2009 HHR come into the shop with a persistent P0302 (Cylinder 2 Misfire) code. The owner had already replaced the spark plug, ignition coil, and fuel injector, but the misfire wouldn’t go away. After hooking up our diagnostic scope, we noticed the control signal from the PCM to the #2 injector was weak and erratic. The internal driver in the original PCM had failed. We installed one of our VIN-programmed modules, performed the security relearn, and the HHR ran perfectly. The customer had spent hundreds on parts they didn’t need before finding the true source of the problem.
Common Symptoms of a Failing 2007-2011 HHR PCM
- ✔ Persistent Check Engine Light (CEL) with various codes
- ✔ Engine stalling, stumbling, or hesitating during acceleration
- ✔ Rough or erratic idling
- ✔ A sudden and unexplained drop in fuel economy
- ✔ No-start or hard-starting conditions
- ✔ Transmission shifting problems or harsh shifts
- ✔ Failure to communicate with diagnostic scan tools
- ✔ False sensor failure codes that return after replacement
The Importance of VIN Programming
Your vehicle’s VIN is more than just a serial number; it’s a blueprint that details the specific engine, transmission, emissions system, and options your car was built with. Programming this 2007-2011 HHR PCM with your VIN ensures all these parameters are correctly loaded. This critical step guarantees that the engine receives the precise amount of fuel and spark at the right time, the transmission shifts smoothly, and all onboard systems communicate correctly. Attempting to install a non-programmed module will result in a no-start condition and potential damage to other electronic components.
This module is a direct replacement for multiple service numbers, including 12597125, 12612397, 12594750, 12629019, 12635902, and 12611549. By providing your VIN, we ensure you receive a perfectly matched and updated computer for your specific application.
Simple Installation Process
Once you receive your pre-programmed module, the physical installation is straightforward. After swapping the hardware, you will need to perform a simple security relearn procedure, which can typically be done without special tools. This procedure pairs the new PCM with your vehicle’s anti-theft system. Instructions are readily available online or in service manuals. This final step is all that’s needed to get your HHR back on the road and running like new.
Frequently Asked Questions
Do I need to have this programmed by a dealer?
No. We handle the programming for you before the part is shipped. Simply provide your vehicle’s VIN during or after checkout, and it will arrive ready for installation and a security relearn procedure.
What is a security relearn procedure?
It’s a simple process that syncs the new PCM with your vehicle’s existing anti-theft system and keys. It typically involves a sequence of turning the key in the ignition and waiting for specific intervals. It does not require a professional scan tool.
How do I find my VIN?
Your 17-digit VIN can be found on your vehicle’s registration, insurance card, or on a metal plate on the driver’s side of the dashboard, visible through the windshield.
Is this part compatible with other GM vehicles?
Yes, this PCM fits a wide range of GM models and years, including certain Cobalt, Malibu, G6, Silverado, and Sierra models. Please refer to the detailed fitment list on this page to confirm compatibility with your specific vehicle and engine.
What causes a PCM to fail?
PCM failure can be caused by a variety of factors, including electrical shorts, voltage spikes from a bad alternator or jump-start, excessive heat, and moisture intrusion. It’s always a good practice to check your battery and charging system when replacing a PCM.