Maintaining your 2008 Subaru Impreza in top condition often involves routine maintenance, and sometimes, disconnecting the car battery becomes necessary. However, disconnecting the battery can lead to a reset of your car’s learned settings, radio presets, and clock. For Subaru Impreza owners, understanding the OBDII port and its power capabilities is crucial, especially when trying to avoid these resets. Let’s delve into the specifics of your 2008 Subaru Impreza’s OBDII port.
The Importance of Constant Power and Memory Retention
Modern vehicles, including the 2008 Subaru Impreza, rely on various control modules to manage engine performance, transmission, and other systems. These modules often store learned data to optimize your car’s operation. When battery power is interrupted, these volatile memories can be erased, leading to temporary inefficiencies as the car relearns. Beyond engine management, simple conveniences like your saved radio stations and clock settings are also lost.
Accessory Outlets: Not a Reliable Solution for Subarus
In some vehicles, the accessory power outlet remains powered even when the ignition is off. This allows mechanics and owners to connect a 12V power source to maintain system memory while the main battery is disconnected. Unfortunately, this isn’t the case with Subaru vehicles like the 2008 Impreza. Their accessory outlets are not constantly powered, making this common technique ineffective.
Utilizing the OBDII Port: Pin 16 for Power Supply
For Subaru Impreza owners seeking a solution to maintain power during battery disconnection, the On-Board Diagnostics II (OBDII) port offers an alternative. Specifically, pin 16 of the OBDII connector is designed to be constantly powered. This provides a potential access point to supply temporary power to your car’s system, preserving those crucial memory settings.
Many automotive service centers utilize specialized adapters to connect an external 12V power source, such as a jump starter, directly through the OBDII port. This method, when executed correctly and cautiously, can prevent data loss during battery changes. It’s important to note that this connection often utilizes a 7.5 Amp fuse for safety.
Cautions When Using the OBDII Port for Power
While the OBDII port’s pin 16 can be a helpful solution, it’s essential to proceed with caution. The 7.5 Amp fuse in the circuit is designed to protect the system from overloads. If any electrical components within the car are activated while the battery is disconnected and power is supplied through the OBDII port, the current draw could exceed 7.5 Amps. Even something as simple as opening a door and activating the interior lights could cause a surge in current.
If this current limit is surpassed, the 7.5 Amp fuse will blow. The consequence of a blown fuse in this scenario is the same as if you had simply disconnected the battery without any power maintenance – your radio presets, clock, and learned ECU data will be lost.
This issue is a common occurrence, even for experienced technicians. The telltale signs are a reset clock and radio, and possibly a period of rough idling after reconnecting the battery as the engine control module (ECM) goes through its relearning process. It’s conceivable that a service shop attempting to maintain power through the OBDII port during a battery replacement might inadvertently trigger a fuse blow by activating a car function.
Importantly, a blown fuse in this context is not related to Check Engine Lights (CELs) and will not trigger one. However, if a code reader relies on the car’s power through the OBDII port to operate, a blown fuse will prevent it from functioning and reading any stored diagnostic trouble codes.
Conclusion: Approach with Care
Maintaining power through the 2008 Subaru Impreza’s OBDII port (pin 16) during battery disconnection is a viable technique to prevent memory loss. However, it demands careful execution and awareness of the potential for overloading the 7.5 Amp fuse. By understanding these limitations and proceeding cautiously, you can effectively use the OBDII port to preserve your car’s settings during battery service.
