Okay, I have a 2001 Ford Focus. Engine light was on. It threw codes P0135 and P0141. Easy enough, so I replaced the O2 sensors. Light went off in park. Drove around the block, back on. Same codes. Checked fuse 18, and it seemed okay. So, someone suggested I replace the plug wires. Did that. No change. So, I'm open to suggestions. If it is wiring, are there any instructions on how to check that? If it's PCM, could I just replace the chip in it? What's the cheapest options here. Ford says 800 dollars. Please help! I can't get a tag until this thing passes emissions.