I'm an idiot and forgot to disconnect the negative lead on my battery yesterday before welding the exhaust. The code clears after removing the neg lead and reattaching, but comes back after driving for a bit. I noticed the sound when turning the key to the ON position before turning it over. I'm thinking I fried something in or around my ECM/PCM and am afraid I'll need a dealer to diagnose and program a new one. Car is an '06 2.5L 4 cylinder Altima S, manual transmission. Link to youtube is a video I took on my phone that recorded the sound.