Maintaining your vehicle’s computer memory during battery disconnection is crucial to prevent the loss of important settings and engine performance parameters. For 1999 Subaru Forester owners, accessing the On-Board Diagnostics II (OBD2) port can be a key step in this process. This guide provides a detailed explanation of the OBD2 port location in your 1999 Subaru Forester and its potential use for memory preservation.
Why is Maintaining Power Important When Disconnecting Your Battery?
When you disconnect your car battery, you interrupt the power supply to various electronic control modules. These modules store “learned” data that optimizes your car’s performance. This data includes settings for the engine control unit (ECU), transmission control unit (TCU), and even radio presets and clock settings.
Losing power can lead to:
- Loss of Radio Presets and Clock Settings: These are the most immediately noticeable inconveniences.
- Engine Performance Issues: The ECU may need to “relearn” optimal settings for idle, fuel trim, and emissions, potentially causing rough idling or reduced fuel efficiency temporarily.
- Transmission Shifting Problems: Similar to the engine, the TCU may need to relearn shift points, affecting transmission performance.
Therefore, maintaining a temporary power supply while the battery is disconnected can prevent these issues and ensure a smoother transition.
The OBD2 Port: A Potential Power Source for Memory Maintenance
For many vehicles, including the 1999 Subaru Forester, the OBD2 port offers a convenient access point to the car’s electrical system, even when the battery is disconnected. Specifically, pin 16 of the OBD2 port is designed to be constantly powered. This makes it a potential location to connect an external 12V power source to preserve vehicle memory.
However, it’s important to note that unlike some vehicles where accessory outlets remain powered, Subaru Forester outlets are typically not constantly powered. This makes the OBD2 port a more viable alternative for maintaining memory during battery changes.
Finding the OBD2 Port in Your 1999 Subaru Forester
Locating the OBD2 port is the first step to utilizing it for memory preservation. For the 1999 Subaru Forester, the OBD2 port is typically found in the driver’s side footwell area.
Step-by-Step Location Guide:
- Driver’s Side Footwell: Get into the driver’s seat and locate the area beneath the steering wheel and above the pedals. This is the general vicinity of the OBD2 port.
- Dashboard Lower Trim Panel: Look for the lower trim panel of the dashboard, near your right knee when seated.
- Port Orientation: The OBD2 port is usually mounted facing downwards or slightly outwards for easy access.
- Visual Search: Look for a trapezoidal, 16-pin female connector. It is often black or sometimes another dark color and may have a dust cover.
Once you have located the OBD2 port, you can proceed with connecting a memory saver device if you choose to do so.
Important Considerations When Using the OBD2 Port for Power
While the OBD2 port can be used to supply temporary power, it’s crucial to understand the limitations and safety precautions.
Fuse Safety
The circuit powering the OBD2 port is typically protected by a fuse, often a 7.5 Amp fuse. This fuse is designed to protect the system from overcurrent. When using the OBD2 port to maintain memory, you are essentially running the car’s essential electronic systems on this fuse.
Avoiding Power Overdraw
It is imperative to ensure that no high-current devices are activated in the car while using the OBD2 port for power. Even seemingly minor loads can cause issues:
- Interior Lights: Opening a door can activate interior lights, which can draw several amps of current.
- Headlights/Parking Lights: Accidentally switching on any exterior lights will draw significant current.
- Ignition Switch: The ignition must remain in the “OFF” position.
If the current draw exceeds the 7.5 Amp fuse rating when the car battery is disconnected and power is supplied through the OBD2 port, the fuse will blow. This will result in the loss of memory, just as if the OBD2 port was not used.
Consequences of a Blown Fuse
A blown fuse in this circuit will not typically cause a Check Engine Light (CEL). However, it will prevent an OBD2 code reader from powering up and communicating with the car’s computer if the reader relies on the car’s power.
Conclusion
Locating the OBD2 port in your 1999 Subaru Forester is a straightforward process. Utilizing it to maintain vehicle memory during battery disconnection is a viable technique, but requires caution. Always ensure no unnecessary electrical loads are active to avoid blowing the fuse and defeating the purpose of memory preservation. By understanding the OBD2 port location and these important considerations, you can confidently manage battery changes on your 1999 Subaru Forester and minimize disruptions to your vehicle’s settings and performance.
