Disconnecting your car battery in a 2008 Subaru WRX can lead to more than just a reset clock. Many modern vehicles, including the WRX, rely on constant power to retain crucial settings and learned data within their control modules. Losing this memory can result in inconveniences like radio presets disappearing and, in some cases, temporary rough engine idling as the engine control module (ECM) relearns optimal parameters. Fortunately, your 2008 WRX offers a solution through its OBD2 port.
One common misconception is that using the accessory power outlet to supply power during a battery change will prevent memory loss in Subarus. However, unlike some other car brands, the accessory outlets in a 2008 WRX are not constantly powered. This means you need to find an alternative power source to maintain those important settings. The On-Board Diagnostics II (OBD2) port, specifically pin 16, provides a constant 12V connection directly to the car’s electrical system, even when the ignition is off.
An image depicting the location of the OBD2 port in the driver’s side footwell of a 2008 Subaru WRX, highlighting its accessibility for connecting a memory saver device during battery replacement.
Many automotive service centers utilize this feature by employing adapters that connect a 12V power source, such as a jump starter or battery maintainer, to the OBD2 port. This effectively back-feeds power into the system, allowing you to disconnect the battery without erasing the vehicle’s learned settings. This method is generally safe and effective, provided you adhere to a critical precaution: ensure nothing in the car is turned on during the battery replacement process.
The OBD2 port circuit is typically protected by a 7.5 Amp fuse. This fuse is designed to handle the minimal current draw required to keep the control modules and memory alive. However, if any electrical accessory is activated – even something as seemingly minor as opening a door and triggering the interior lights – the current demand can spike rapidly. If this demand exceeds the 7.5 Amp fuse rating while the main battery is disconnected, the fuse will blow. The consequence of a blown fuse in this scenario is the same as if you hadn’t used a memory saver at all: you’ll lose your radio presets, clock settings, and potentially experience a temporary rough idle.
A close-up image illustrating a blown 7.5 Amp fuse, emphasizing the importance of not overloading the OBD2 port circuit when using it as a power source during battery changes on a 2008 WRX.
It’s a common, often unintentional mistake. Car owners might not realize that even a brief activation of interior lights can cause a problem. The telltale signs are a reset clock and radio, and possibly a slightly rough engine idle immediately after the battery replacement, which resolves itself as the ECM relearns. It’s plausible that a technician attempting to maintain power through the OBD2 port might inadvertently trigger an accessory, leading to the 7.5 Amp fuse blowing.
It’s crucial to understand that this fuse is not related to any Check Engine Light (CEL) issues. A blown OBD2 port fuse will not trigger a 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 through the OBD2 port. Therefore, if you are planning to read diagnostic codes after a battery change and your reader is not powering on, checking the 7.5 Amp OBD2 port fuse should be one of your first steps.
In conclusion, utilizing the OBD2 port on your 2008 Subaru WRX is a viable method for preserving vehicle settings during battery replacement. However, always remember the 7.5 Amp fuse limitation and ensure all electrical accessories are turned off to prevent accidental fuse failure and the very memory loss you are trying to avoid.
