For 2019 Subaru Forester owners, understanding your vehicle’s systems is key to proper maintenance. One important component for diagnostics and even battery replacement is the OBD2 port. This port is your gateway to your car’s computer, allowing mechanics and even you to read diagnostic trouble codes and access important vehicle data. But when it comes to tasks like battery replacement on a 2019 Subaru Forester, the OBD2 port can play an unexpected role in preserving your car’s settings.
Typically, when a car battery is disconnected, various control modules lose power. This can erase “learned” data that optimizes your car’s performance. You might also lose radio presets and clock settings. In some vehicles, you can use the accessory power outlet to maintain power while changing the battery. However, Subaru Foresters, including the 2019 model, usually don’t have constantly powered accessory outlets. This means you need to find an alternative to keep those settings intact.
The OBD2 port, specifically pin 16, offers a solution. This pin is designed to be always powered, providing a constant 12V connection to the car’s electrical system. This constant power is intended for diagnostic tools, but it can be cleverly used to supply temporary power during a battery change, preventing memory loss.
Many auto service centers utilize adapters that connect a 12V power source, like a jump starter, through the OBD2 port. This connection, often protected by a 7.5 Amp fuse in the adapter, keeps the car’s computer and memory powered while the main battery is disconnected. This method works effectively as long as you avoid turning on any power-hungry accessories within the car. The modules requiring power to maintain memory draw very little current, well within the 7.5 Amp fuse limit.
However, a common mistake can lead to a blown fuse. If a door is opened, activating interior lights, or if any other significant electrical load is introduced while the OBD2 port is supplying power, the current draw might exceed 7.5 Amps. This will blow the fuse, effectively cutting power and resulting in the same memory loss you were trying to prevent – reset clock, radio presets, and potentially a slightly rough idle as the engine control module (ECM) relearns its parameters.
It’s plausible that if you’ve experienced these resets after a battery service, the technician may have attempted to use the OBD2 port for power maintenance but inadvertently overloaded the circuit, blowing the fuse. It’s crucial to understand that this blown fuse is not related to check engine lights (CELs) and won’t trigger one. However, it will prevent a code reader that relies on the car’s power from operating correctly if the fuse is blown.
In summary, the OBD2 port on your 2019 Subaru Forester, located typically under the dashboard on the driver’s side, can be a useful point for maintaining vehicle memory during battery replacement. Knowing its location and understanding the precautions related to power draw can help ensure a smooth battery change without losing your car’s important settings. Just remember to avoid any unnecessary electrical load during the process to prevent blowing the protective fuse.
