Disconnecting your car battery in a 2012 WRX can lead to more than just a simple power loss. Modern vehicles, including the Subaru WRX, rely on constant power to retain crucial data within their control modules. This “learned” data optimizes your car’s performance and manages settings like your radio presets and clock. When battery power is interrupted, these settings are lost, potentially impacting your driving experience.
While some vehicles offer a workaround using the accessory power outlet to maintain system memory during battery changes, this method is ineffective for Subarus like the 2012 WRX. This is because the accessory outlets in these models are not constantly powered. So, where can you turn to maintain power and avoid losing your 2012 WRX’s settings? The answer lies within your car’s On-Board Diagnostics (OBD2) connector.
The OBD2 connector, specifically pin 16, provides a constant power source directly from your car’s electrical system. This makes it a viable point for connecting an external 12V power supply when disconnecting the main battery. Automotive service centers frequently utilize this method, employing specialized adapters to connect a 12V source, such as a portable jump starter, through the OBD2 port. This process is typically protected by a 7.5 Amp fuse in the vehicle’s electrical system.
This technique effectively preserves your 2012 WRX’s memory as long as all electrical accessories are turned off during the battery disconnection. The modules requiring constant power draw only a minimal current, well within the 7.5 Amp fuse rating. However, activating any electrical component, even something as simple as opening a door and turning on the interior lights, can drastically increase the current draw. If this increased current exceeds 7.5 Amps while the car battery is disconnected, the fuse will blow – as designed – to protect the system.
If the fuse blows during this process, the result is the same as if no power maintenance was attempted at all: you’ll lose your radio presets, clock settings will reset, and the engine control module (ECM) might exhibit rough idling until it “relearns” optimal parameters. It’s quite possible that a blown fuse during a battery replacement is a common, albeit unintentional, occurrence in workshops. Technicians attempting to maintain power through the OBD2 port might inadvertently trigger a fuse failure by switching on an accessory.
It’s important to note that this fuse is unrelated to your car’s Check Engine Light (CEL). A blown fuse will not trigger a CEL. However, a blown fuse will prevent a standard OBD2 code reader from functioning if the reader relies on the car’s power supply to operate. Therefore, if you encounter a non-responsive code reader after a battery service, checking this fuse is a worthwhile diagnostic step, particularly on a 2012 WRX where maintaining system memory during battery changes requires careful procedure.
