Is Your Chevrolet HHR Running Rough? The Engine Computer Might Be the Culprit.
If your 2007-2011 Chevrolet HHR is suffering from baffling issues like a persistent check engine light, stalling, poor fuel mileage, or a no-start condition, the problem may lie deep within its electronic nervous system: the Powertrain Control Module (PCM). As the central brain of your vehicle, the PCM controls everything from fuel injection and ignition timing to transmission shifting and emissions. When it fails, it can create a cascade of problems that are often misdiagnosed, leading to costly and unnecessary repairs.
This replacement PCM, corresponding to service number 12635902, is the definitive solution to restore your vehicle’s performance and reliability. We take the guesswork out of the repair by pre-programming the module specifically to your vehicle’s Vehicle Identification Number (VIN). This ensures that all factory settings, security protocols, and operational parameters are perfectly matched to your HHR’s unique configuration, making for a seamless installation process.
From the Diagnostic Bay
We once had a 2009 HHR come into the shop that had its owner at his wit’s end. He’d replaced the spark plugs, ignition coils, and even the mass airflow sensor trying to chase down an intermittent stalling problem and a P0606 (Internal Control Module Processor Error) code. The car would run fine for days, then suddenly die at a stoplight. After confirming power and ground to the module were solid, we swapped in a programmed PCM. The stalling vanished instantly. It was a classic case of a failing processor inside the original computer that was causing unpredictable shutdowns. The customer had spent hundreds on parts he didn’t need before addressing the actual source of the problem.
Common Symptoms of a Failing PCM
- ✔ Persistent Check Engine Light (CEL) that won’t clear, often with communication error codes (U-codes) or internal processor codes (P06xx).
- ✔ Unexplained engine stalling or rough idling.
- ✔ Intermittent no-start or hard-starting conditions where the engine cranks but won’t fire up.
- ✔ A noticeable decrease in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Failure to pass state emissions inspections.
- ✔ Other warning lights, like the traction control or security light, illuminating randomly.
The Right Solution: A Pre-Programmed 2007-2011 HHR PCM
Don’t settle for a generic, unprogrammed module that will require an expensive trip to the dealership for flashing. This unit is a direct-fit replacement for a wide range of GM vehicles and is guaranteed to be compatible if your original module carries any of the following service numbers: 12635902, 12597125, 12612397, 12594750, 12629019, or 12611549. By providing us with your VIN during checkout, we load the latest GM-certified software onto the module. This process ensures your vehicle benefits from any performance, efficiency, and drivability improvements released by the manufacturer since your car was new. The result is a straightforward repair that you can often complete in your own driveway.
Installation is Simple
While professional installation is always an option, replacing the PCM is typically a manageable task. After disconnecting the battery, you’ll locate your old module (in the HHR, it’s in the left rear of the engine compartment), carefully disconnect the wiring harnesses, unbolt the unit, and install the new one in its place. Once reconnected, your vehicle may require a simple security relearn procedure, which can often be done without special tools. This procedure pairs the new computer with your vehicle’s anti-theft system. Instructions for this are widely available online or in vehicle service manuals.
Frequently Asked Questions
What is the difference between a PCM and an ECM?
The terms are often used interchangeably. ECM stands for Engine Control Module, while PCM stands for Powertrain Control Module. A PCM is a more advanced type of ECM that also controls the transmission and other powertrain components, which is standard on most modern vehicles like your HHR.
Do I need to have this programmed by a dealer?
No. The main benefit of our service is that we program the module to your car’s specific VIN before we ship it. This means it arrives ready to be installed, saving you the time and expense of a dealership visit.
How do I find my vehicle’s VIN?
Your 17-digit VIN can be found on the driver’s side of the dashboard (visible through the windshield), on the driver’s side door jamb sticker, or on your vehicle’s registration and insurance documents.
What happens if I install this without a security relearn?
In most cases, the vehicle’s anti-theft system will prevent the engine from starting. The security light on your dashboard will likely flash. A security relearn procedure is a necessary final step to sync the new PCM with your vehicle.
Will this PCM fit vehicles other than the HHR?
Yes. This module is compatible with a wide variety of GM models, including the Chevrolet Cobalt, Malibu, Silverado 1500, Pontiac G5/G6, Saturn Aura, and more. Please verify that your original part number is listed as compatible.