When you disconnect your car battery in a vehicle like the 2015 WRX, you might not realize that you’re also cutting power to various control modules. These modules often store learned data that optimizes your car’s performance. Beyond performance, simple conveniences like your radio presets and clock settings are also at risk of being erased when power is lost. Many modern vehicles are designed to maintain power to these systems even when the main battery is disconnected. Some cars achieve this through constantly powered accessory outlets, allowing a 12V supply to be connected to preserve these settings during battery changes.
However, for 2015 Subaru WRX owners, relying on the accessory outlet for this purpose is not an option as they are not constantly powered. This necessitates finding an alternative power source to maintain these crucial settings. One viable option is the OBD2 connector, specifically pin 16, which is designed to be always hot, providing a constant connection to the vehicle’s electrical system. This constant power feed through the 2015 Wrx Obd2 Interface becomes a lifeline for your car’s memory when the battery is disconnected.
Many automotive service centers utilize this 2015 WRX OBD2 interface approach by employing adapters that connect a 12V power source, such as a portable jump starter, via the OBD connector and a 7.5 Amp fuse. This method effectively supplies power to the car’s electrical system, enabling battery disconnection without memory loss. This works seamlessly as long as no power-intensive accessories are activated within the vehicle. The modules requiring constant power draw very minimal amperage, well within the 7.5 Amp fuse rating.
The problem arises if a door is opened, activating interior lights, or if any other significant electrical load is introduced while the car battery is disconnected and powered through the 2015 WRX OBD2 interface. These lights, or other accessories, can easily draw current exceeding the 7.5 Amp fuse’s capacity. If this happens, the fuse will blow, as designed, to protect the system. The consequence of a blown fuse in this scenario is the same as if no power maintenance was attempted – the radio presets, clock, and learned module data will be lost, essentially defeating the purpose of using the OBD2 interface for power maintenance during battery changes.
This inadvertent fuse blowing is a common occurrence and is often first noticed by the reset clock and radio. In some cases, especially in a 2015 WRX, you might experience rough idling for a short period after reconnecting the battery. This is because the Engine Control Module (ECM) needs to “relearn” certain parameters to optimize engine performance. It’s plausible that if you’ve had a battery replacement service and experienced these resets, the technician might have attempted to maintain power through the 2015 WRX OBD2 interface but inadvertently triggered an accessory, leading to the fuse blowing.
It’s crucial to understand that this 7.5 Amp fuse, related to maintaining power via the 2015 WRX OBD2 interface, is not connected to the Check Engine Light (CEL) system. A blown fuse in this circuit will not trigger a CEL. However, it will prevent an OBD2 code reader from operating if the reader relies on the car’s power supply through the 2015 WRX OBD2 interface to function. Therefore, when working with your 2015 WRX, especially during battery changes, understanding the nuances of the OBD2 interface and its power limitations is key to avoiding data loss and potential minor inconveniences.
