The OBD2 port on a 1999 Subaru Legacy Outback, like in most vehicles, plays a crucial role in diagnostics. However, it can also be utilized to maintain power to certain modules while disconnecting the battery. This prevents the loss of learned data, radio presets, and clock settings, which typically occurs when the battery is disconnected. Unlike some vehicles, Subaru accessory power outlets are not constantly powered, necessitating alternative methods for preserving these settings.
Utilizing the OBD2 Port for Power
On a 1999 Subaru Legacy Outback, the OBD2 port offers a solution. Pin 16 of the connector provides a constant 12V power source. Many service centers employ adapters that connect a 12V source, like a portable battery, to the OBD2 port via this pin, often using a 7.5 amp fuse for protection.
This method effectively powers the necessary modules, consuming minimal current. However, caution is advised. Activating any significant electrical load, such as interior lights by opening a door, can exceed the 7.5 amp fuse capacity. A blown fuse results in the same data loss as a complete battery disconnect – resetting the clock, radio presets, and potentially causing rough idling until the Engine Control Module (ECM) relearns its parameters.
Potential Issues and Considerations
A common scenario is inadvertently blowing this fuse during battery replacement. Even a momentary activation of car accessories can overload the circuit. While a blown fuse in this context won’t trigger a Check Engine Light (CEL), it can prevent OBD2 code readers from functioning if they rely on the vehicle’s power. Using a code reader with its own independent power source can circumvent this issue.
Locating the OBD2 Port
The OBD2 port in a 1999 Subaru Legacy Outback is typically located under the driver’s side dashboard, near the steering column. It’s a standardized trapezoidal connector. Consult your owner’s manual for the precise location if needed.
This method of maintaining power through the OBD2 port offers a convenient solution for preserving vehicle settings during battery disconnection. However, awareness of the fuse limitation and potential for accidental overload is crucial for preventing unintended data loss. Always exercise caution when working with electrical systems in your vehicle.
