Maintaining your Subaru WRX’s computer memory during a battery change is crucial. Disconnecting the battery can erase important learned settings for optimal engine performance, along with your radio presets and clock. While some vehicles allow you to use the accessory power outlet to prevent this memory loss, Subaru WRXs are different – their outlets aren’t constantly powered. A common workaround is using the OBD2 port, specifically pin 16, which is always hot, to supply temporary power during battery swaps.
Many DIYers and even some service centers use adapters to connect a 12V power source to the OBD2 port to keep everything powered up. This method usually works because the modules needing power draw very little current. However, a frequent issue arises from a small but critical detail: the 7.5 Amp fuse protecting this circuit.
The problem occurs when something in the car is inadvertently turned on while the battery is disconnected and power is supplied through the OBD2 port. Even opening a door can trigger interior lights, drawing a current that might exceed the 7.5 Amp fuse limit. If this happens, the fuse blows, effectively cutting off power and defeating the purpose of using the OBD2 port in the first place.
The immediate consequence is the same as if you hadn’t used the OBD2 port at all – your clock and radio reset, and the engine’s computer (ECM) might need to relearn its optimal settings, sometimes causing rough idling temporarily.
It’s quite possible that if you’re experiencing a “Wrx Obd2 Port Not Working” situation after a battery replacement, a blown fuse is the culprit. Perhaps during a battery change, a door was opened, or the ignition was briefly turned on while power was being supplied through the OBD2 port.
Crucially, a blown fuse in this circuit won’t trigger a Check Engine Light (CEL). However, it will prevent your OBD2 code reader from powering up and communicating with the car’s computer if it relies on the car’s power through the OBD2 port. This is because pin 16, the power supply pin, is now dead due to the blown fuse.
Troubleshooting a Non-Functioning WRX OBD2 Port After Battery Work:
If your OBD2 port seems dead after battery service, especially if your code reader won’t power on, the first and simplest thing to check is the 7.5 Amp fuse associated with the OBD2 port power supply.
- Locate the Fuse Box: Consult your WRX owner’s manual to find the location of the interior fuse box. It’s often under the dashboard or in the glove compartment.
- Identify the Correct Fuse: Refer to the fuse box diagram in your owner’s manual or on the fuse box cover itself. Look for the fuse labeled “OBD,” “Diagnostic,” or similar, and confirm it’s a 7.5 Amp fuse.
- Inspect the Fuse: Carefully remove the fuse. You can usually do this with your fingers or needle-nose pliers. Hold the fuse up to the light and check the thin wire inside. If the wire is broken or the plastic is blackened, the fuse is blown.
- Replace the Fuse: If the fuse is blown, replace it with a new 7.5 Amp fuse. Ensure you use the correct amperage. Using a higher amperage fuse can cause damage to your car’s electrical system.
- Test Your OBD2 Port: After replacing the fuse, try using your OBD2 code reader again. It should now power up and function correctly, assuming the blown fuse was the only issue.
In conclusion, if you’re facing a “WRX OBD2 port not working” issue, especially following a battery replacement or any work involving battery disconnection, a blown 7.5 Amp fuse is a prime suspect. Checking and replacing this fuse is a quick, easy, and often overlooked fix that can get your OBD2 port back online and your diagnostic capabilities restored. Remember to minimize power draw when using the OBD2 port for memory keeping during battery changes to prevent this issue in the future.
