Intermittant 'service engine soon' AND spkr performance

[graybmg]

Wondering if the two could possibly be interrelated or how to fix either one. The Service Engine Soon light glows steady for a day or two then it goes off for a day or two. Service dept. wants to charge me $450 for a new sensor. But for what??? Not convinced there is a real problem.

Coincidentally, my base stereo speakers have one by one shut down. I went from 10 working speakers to three and now back up to five. Rear one is blown. I listen to it loud but still dissappointed that I blew it that quickly. Why would they come on and off? It's like a fuse is messed up or something.

Is there any way in heck the two could be related or does anyone have any advice on fixing the two independently?

Thanks for your help. It's a 2001 325i with 90,000 miles. ( i commute a long way) Nevermind that I'm on the verge of insanity from the various squeaks. Fun car to drive though.