Disconnecting your car battery is a common procedure for various maintenance tasks, from replacing the battery itself to working on electrical components. However, for owners of a 2015 Subaru WRX, simply disconnecting the battery can lead to more than just a reset clock. Modern vehicles, including the 2015 WRX, rely on constant power to retain crucial settings and learned data within their control modules. This article will explore why this happens and how utilizing your 2015 Wrx Obd2 Interface can help maintain these important settings.
When your 2015 WRX is running smoothly, much of its performance is attributed to adaptive learning. The engine control module (ECM) and other systems constantly monitor and adjust parameters to optimize engine performance, fuel efficiency, and even transmission shift points. This “learned” data is stored in volatile memory, meaning it requires constant power to be retained. Disconnecting the battery cuts off this power supply, leading to a loss of this learned information. Beyond performance data, simpler conveniences like your radio presets and clock settings are also lost, requiring you to reprogram them after reconnecting the battery.
For many vehicles, there’s a straightforward solution: using the accessory power outlet (cigarette lighter port) to supply temporary power while the battery is disconnected. However, Subaru vehicles, including the 2015 WRX, typically do not have constantly powered accessory outlets. This means you can’t rely on this method to maintain your car’s memory.
Fortunately, the 2015 WRX OBD2 interface offers an alternative power source. Pin 16 of the OBD2 connector is designed to be always powered, providing a direct link to the car’s electrical system, even when the ignition is off. This constant power supply is primarily intended for diagnostic tools, but it can also be cleverly utilized to maintain vehicle memory during battery changes or disconnections.
Many automotive service centers are aware of this and employ specialized adapters. These adapters connect a 12V power source, such as a jump starter or battery maintainer, directly to the OBD2 port, specifically pin 16. By doing so, they ensure a continuous power flow to the car’s systems, even with the main battery disconnected. A common practice is to use a 7.5 Amp fuse in this circuit as a safety measure.
It’s crucial to remember a key precaution when using the 2015 WRX OBD2 interface for this purpose: ensure all vehicle accessories are turned off. The 7.5 Amp fuse is designed to protect the system from overload. While the power draw from the control modules is minimal, activating accessories like interior lights, headlights, or even opening a door (which can trigger dome lights) can significantly increase the current draw. If this draw exceeds 7.5 Amps while the battery is disconnected and power is being supplied through the OBD2 port, the fuse will blow. This effectively defeats the purpose, resulting in the same memory loss as if no power maintenance was attempted.
A blown fuse in this scenario is often noticed by the reset clock and radio presets after reconnecting the battery. You might also experience slightly rough idling for a short period as the ECM needs to “relearn” optimal settings. In some cases, a technician attempting to maintain power via the OBD2 port might inadvertently trigger an accessory, leading to this blown fuse and unintended memory loss.
It’s important to note that this fuse is not related to the check engine light (CEL) system and will not cause a CEL if blown. However, a blown fuse in this power maintenance circuit will prevent an OBD2 code reader from functioning if it relies on the car’s power to operate. This is because pin 16, which provides power to the reader, will be inactive due to the blown fuse.
In conclusion, understanding the 2015 WRX OBD2 interface and its pin 16 constant power supply is valuable for maintaining your vehicle’s memory during battery disconnection. By carefully utilizing this method and ensuring no accessories are active, you can avoid the inconvenience of resetting your car’s settings and allow your 2015 WRX to continue performing optimally without the need for extensive relearning periods after a battery change.
