I'm sure most here have a love/hate relationship with mechanics. Love when they fix the car, hate when you get the bill (harhar). Anyways, the Check Engine light in my car came on at 155k. I just knew my usual mechanic would charge me an arm and a leg for probably something relatively small so I did some searching on the net. It turns out you can put your ECU into a diagnostic mode which will flash the check engine light in numerical pattens, giving you a 4-digit code (for my car anyway). So I did it and took this number to a site that's a big database for all 4th generation Maxima codes. Turns out it was a faulty knock sensor, a common problem with my year. Some more searching led me to several DIY repair guides with pics included. They also said where I can get the sensor for $95, as opposed to $168.50 which is usually what the mechanic would charge. So I got the sensor but had reservations about installing it since I've never done any engine work or repair. I called my mechanic, told him how I got the code fromt the internet guides and all. He answered back in a condescending tone saying that you should never trust those and he'd have to run a full diagnostic test for $75. I said thanks for your time and hung up. So let's see: $75 + $168.50 + $50 labor + tax!? No way, well not yet anyway. I ended up taking about an hour doing it myself. Got a still-painful manly gash on my right hand but it was worth $200. So now the Check Engine light turned off by itself after about a day and my car accelerates much better below 3k RPM. Next up; replacing brakes!