1999 Honda Civic Check Engine Light On with P0135 Code: How to Troubleshoot O2 Sensor and Fuse Issues

Hi, I own a 1999 Honda Civic EX and recently the check engine light has come on. I replaced the upstream oxygen sensor myself about two years ago, and I recently changed it again with a Bosch part from Advanced Auto Parts. After driving approximately 100 miles, the check engine light remains illuminated. The car runs smoothly with no noticeable performance issues—such as power loss, stalling, or malfunctioning windows or doors. I’ve noticed that when I turn the key to the ignition (without starting the engine), the check engine light turns on, then after about 2 seconds there’s a distinct click sound from inside the driver's seat, followed by a single blink of the light before it returns to solid on. This behavior is consistent. I’ve read that fuse issues can also trigger the P0135 code, especially in older models like mine. Since I’ve already replaced the O2 sensor and the car runs fine, I’m wondering if there’s a deeper issue—such as a faulty wiring connection or a blown fuse—that could be causing this. I’d like to know how to properly troubleshoot the fuse and electrical circuit related to the P0135 code. While I’ve been trying to save money by doing repairs myself, I’m concerned about using aftermarket parts. My previous O2 sensor replacement used a Bosch unit, but I’m now considering whether OEM sensors would be more reliable for this specific model. Any advice on diagnosing or fixing the P0-135 issue in a 1999 Honda Civic EX would be greatly appreciated. I’d prefer to attempt repairs myself if possible, as mechanics charge high fees. Thanks, Prashant