Changing your car battery is a routine maintenance task, but for 2009 Subaru Forester owners, disconnecting the battery can lead to more than just a jump start. Like many modern vehicles, your Subaru Forester relies on constant power to retain crucial settings for its various control modules, radio presets, and clock. Losing this power can result in lost data, impacting your car’s optimal performance and convenience.
Why Battery Disconnection Resets Your Subaru’s Settings
Modern cars, including the 2009 Subaru Forester, utilize sophisticated electronic control units (ECUs) and modules that “learn” and adapt over time to optimize engine performance, transmission shifts, and other functions. This learned data, along with user preferences like radio stations and clock settings, is preserved by a constant power supply from the battery. When the battery is disconnected, even for a short battery replacement, this power is interrupted. This power loss leads to a reset of these learned settings and presets.
The OBD2 Port Solution for Your 2009 Subaru Forester
Fortunately, there’s a way to prevent this memory loss when replacing the battery in your 2009 Subaru Forester. The On-Board Diagnostics II (OBD2) port, typically used for diagnostic scanning and code reading, can also serve as a temporary power source. Pin 16 of your Subaru Forester’s OBD2 connector is designed to be always powered, providing a direct link to the car’s electrical system, even when the battery is disconnected.
Pin 16: Your Power Source
By utilizing pin 16, you can supply external power to your 2009 Subaru Forester’s electrical system while the main battery is disconnected. This prevents the loss of volatile memory in the control modules, radio, and clock.
Using an OBD2 Memory Saver – Step-by-Step
To maintain power during a battery change, you can use an OBD2 memory saver device or a 12V power source with an appropriate adapter. Here’s a general procedure:
- Prepare your power source: Use a dedicated OBD2 memory saver, a jump starter with a 12V output, or another reliable 12V battery source.
- Locate the OBD2 port: In a 2009 Subaru Forester, the OBD2 port is typically located under the dashboard on the driver’s side.
- Connect the power source: Carefully connect the OBD2 memory saver or your 12V power source to the OBD2 port, ensuring a secure connection.
- Disconnect the car battery: Once the external power is connected through the OBD2 port, you can safely disconnect and remove the old car battery.
- Replace the battery: Install the new car battery.
- Reconnect the battery terminals: Securely reconnect the battery terminals to the new battery.
- Disconnect the memory saver: After the new battery is installed and connected, disconnect the OBD2 memory saver.
Important Considerations and Safety Tips
While using the OBD2 port is a convenient solution, it’s crucial to understand the limitations and safety precautions:
Fuse Protection: 7.5 Amp Limit
The circuit powering the OBD2 port is typically protected by a 7.5 Amp fuse in a 2009 Subaru Forester. This fuse is designed to protect the system from overloads. It’s essential not to exceed this amperage limit when using an external power source.
Avoid Activating Car Accessories
When using the OBD2 port for memory saving, ensure that no car accessories are turned on. Even seemingly minor accessories like interior lights, headlights, or the radio can draw significant current. If the total current draw exceeds 7.5 Amps while the car battery is disconnected, the fuse protecting the OBD2 port circuit will likely blow. This defeats the purpose of memory saving and is a common oversight.
Potential Issues and Troubleshooting
If the 7.5 Amp fuse blows during this process, you will experience the same memory loss as if you had simply disconnected the battery without any power backup. You’ll know if the fuse has blown if your radio and clock are reset after reconnecting the battery. A blown fuse will not trigger a Check Engine Light (CEL), but it will prevent an OBD2 code reader that relies on car power from functioning until the fuse is replaced.
If you suspect the fuse has blown, check the appropriate fuse box in your 2009 Subaru Forester (consult your owner’s manual for location and identification) and replace the blown 7.5 Amp fuse.
Conclusion
Maintaining your 2009 Subaru Forester’s memory during a battery replacement is easily achievable by utilizing the OBD2 port and a memory saver. This simple procedure prevents the inconvenience of resetting your radio, clock, and allows your car to retain its learned settings for optimal performance right after a battery change. By following these steps and safety guidelines, you can ensure a smooth and hassle-free battery replacement for your 2009 Subaru Forester.
