Maintaining your 2009 Subaru Outback’s electrical system during a battery replacement is crucial to prevent data loss from various control modules, radio presets, and the clock. Disconnecting the battery can lead to these memory losses, potentially causing minor inconveniences like resetting your radio stations or, in some cases, affecting engine performance until the car’s computer relearns optimal settings. Fortunately, the OBD2 (On-Board Diagnostics II) connector in your Outback offers a potential solution to provide constant power during battery swaps. This article will guide you through understanding and testing the OBD2 connector on your 2009 Subaru Outback to ensure it can be used for this purpose.
Understanding the OBD2 Connector and Constant Power Supply in Your 2009 Subaru Outback
The OBD2 connector is primarily designed for vehicle diagnostics, allowing mechanics and car owners to access vital information from the car’s computer system using scan tools. However, pin 16 of this connector is intentionally designed to provide a constant 12V power supply directly from the car’s battery. This constant power is essential for the diagnostic tools to function even when the ignition is off. This consistent power source is what makes the OBD2 port a viable, albeit sometimes misunderstood, option for maintaining vehicle memory during battery disconnection on many vehicles, including the 2009 Subaru Outback.
It’s important to note that while some vehicles have always-powered accessory outlets that can be used to maintain power during battery changes, Subaru Outbacks, including the 2009 model, typically do not. This makes the OBD2 connector’s pin 16 a more relevant point of access for this purpose in these vehicles.
Testing Your 2009 Outback’s OBD2 Connector for Constant Power
Before attempting to use the OBD2 connector to supply power during a battery change, it’s critical to test if pin 16 is indeed providing constant power in your specific 2009 Subaru Outback. Variations in vehicle configurations or previous modifications could affect this. Here’s how you can perform a simple test:
- Gather your tools: You will need a multimeter (a digital multimeter is recommended for ease of use).
- Locate the OBD2 connector: In a 2009 Subaru Outback, the OBD2 port is typically located under the dashboard on the driver’s side, often near the steering column.
- Set up your multimeter: Turn on your multimeter and set it to measure DC voltage (usually indicated by “V” with a straight line and dashed line above it). Select a voltage range that can read 12V or higher (e.g., 20V setting).
- Identify pin 16: Refer to an OBD2 connector pinout diagram (easily found online) to correctly identify pin 16. It is typically located in the top row, towards the right side of the connector.
- Connect the multimeter:
- Connect the red (positive) lead of your multimeter to pin 16 of the OBD2 connector. You might need a thin probe to make good contact inside the connector.
- Connect the black (negative) lead of your multimeter to a known good ground point on the vehicle. A bare metal part of the car’s chassis will work, or you can use the negative terminal of the battery if it’s still connected.
- Read the voltage: Observe the voltage reading on your multimeter.
Expected Result: You should read a voltage close to 12V (typically between 12V and 13V, depending on the battery’s charge state) even with the car’s ignition turned completely off. This reading confirms that pin 16 of your 2009 Outback’s OBD2 connector is receiving constant power from the battery.
No Voltage Reading: If you get no voltage reading, double-check your connections and multimeter settings. If you are sure of your setup and still get no reading, it indicates that pin 16 might not be powered in your vehicle, or there could be an issue with the vehicle’s electrical system or a blown fuse related to the OBD2 power supply. In this case, using the OBD2 connector to maintain power is not advisable without further investigation.
Using the OBD2 Connector for Memory Saver During Battery Replacement: Precautions and Procedure
If your test confirms constant power at pin 16, you can cautiously use the OBD2 connector as a power source while replacing your 2009 Subaru Outback’s battery. This method involves using a memory saver device or a 12V power supply connected to the OBD2 port to maintain power to the car’s systems while the main battery is disconnected.
Crucial Precautions:
- Fuse Rating: The OBD2 port’s power supply is typically protected by a fuse, often around 7.5 Amps. It’s vital not to exceed this current draw. Ensure all vehicle accessories (lights, radio, interior lights, etc.) are turned OFF during the battery replacement process. Even opening a door can activate interior lights and potentially draw excessive current, blowing the fuse.
- Memory Saver Device or Safe Power Source: Use a commercially available memory saver device designed for this purpose or a regulated 12V power supply with a current rating that is appropriate and safe for automotive electrical systems. Avoid using high-amperage jump starters directly through the OBD2 port unless specifically designed for memory saving and fused appropriately.
- Procedure Matters: Follow a careful procedure to avoid short circuits or accidental grounding of the positive terminal while the battery is disconnected.
General Procedure (Always refer to your memory saver device’s instructions):
- Prepare your memory saver: Connect your memory saver device to a fresh 9V battery (if battery-powered) or prepare your 12V power supply.
- Connect to the OBD2 port: Carefully plug the memory saver device into the OBD2 connector of your 2009 Outback.
- Verify Connection: Ensure the memory saver is properly connected and, if it has indicator lights, that it shows a successful connection.
- Disconnect the Negative Battery Terminal: Crucially, disconnect the negative battery terminal FIRST from your Outback’s main battery and secure it away from the battery post to prevent accidental contact.
- Disconnect the Positive Battery Terminal: Next, disconnect the positive battery terminal and remove the old battery.
- Install the New Battery: Install the new battery in the reverse order of removal. Connect the positive terminal first, then the negative terminal.
- Disconnect Memory Saver: Once the new battery is securely connected, disconnect the memory saver device from the OBD2 port.
- Verify Functionality: Start your Subaru Outback and check if your radio presets and clock are retained. Also, observe if there are any unusual warning lights or engine performance issues. A slight rough idle immediately after battery reconnection can sometimes occur as the engine control module (ECM) readjusts, but this should quickly resolve.
Potential Risks: Blown Fuse and System Issues
As highlighted in the original article, the most common risk when using the OBD2 connector for this purpose is blowing the fuse that protects the circuit. If any electrical load is inadvertently activated during the battery change process and exceeds the fuse rating (typically 7.5A), the fuse will blow. This effectively defeats the purpose of the memory saver, and you will experience the same memory loss as if you had simply disconnected the battery without any power backup.
A blown fuse in this circuit will not typically cause a Check Engine Light (CEL) but will prevent a code reader from getting power through the OBD2 connector itself, should you need to use one later. If you find your OBD2 port is not powering up a scan tool after attempting this procedure, check the relevant fuse in your Outback’s fuse box (consult your owner’s manual for fuse box diagrams and fuse locations).
Using the OBD2 connector to maintain power during a battery change on a 2009 Subaru Outback can be a useful technique to preserve vehicle settings. However, it requires careful testing, adherence to safety precautions, and awareness of potential risks like blowing the protective fuse. If you are uncomfortable with any part of this procedure or unsure about your vehicle’s electrical system, it is always best to consult a qualified automotive technician.
Alt text: Location of the OBD2 port underneath the dashboard of a vehicle, typically near the steering column, for diagnostic access.
Alt text: Using a digital multimeter to test for constant power at pin 16 of an OBD2 connector, with red lead on pin 16 and black lead grounded to the car chassis.
