Check Engine Light.. Dimmer Switch Code- Please help!
 

A few weeks ago, I had my emissions testing done and passed with no problems. Two days later, I took my 2006 Mazda 3 to the Mazda dealership for the 90,000 mile maintenance and everything supposedly in perfect working order. Within less than a week, my check engine light came on. I check the gas cap and that wasn't causing it. Over the next few weeks, it sporadically turned on and off- at first it seemed related to the temperature outside (i.e. above 55 degrees, it turned off; below, it turned back on). However, then it became obvious it wasn't actually corresponding to the temperature and just would turn on/off randomly, sometimes staying on for a day or a whole week... I finally took the car to the dealership last Thursday and they said the code was for the dimmer switch, and that my dash lights flickered very briefly when the car is turned on... Well, I asked them to show me that because I had never noticed it before and even with the tech in there, I couldn't see anything. They were going to charge me $300 for the part and installation/labor... I decided to wait and get a second opinion because that seemed like a lot of money to spend when there's no other problems seen..

Two days ago, I was idling at a restaurant and heard a buzzing.. it sounded like a belt or maybe a pulley... I am so frustrated and at a loss for what to do!!! How it can be put through emissions testing and then have full maintenance done showing no problems.. never had problems with it in the past... yet the check engine light turns on and off and now there's some noise coming from the engine that was not there before...

Does anyone have any advice for how I should proceed??? Has anyone had any similar problems???