LS1 Service Wrench/E-Brake lights+wiring problems?
 

So I purchased a 2000 LS1 Saturn 2.2L with 123,000 miles 5 months ago. Since then I have put 4,000 miles on it.

I have two(ish) problems and was wondering if someone could tell me if they were related. The service wrench (not service engine soon) came on intermittently but is now is on constantly.
Brake light stays on when the emergency brake is released, however the running lights turn on when brake released (sensor must be good from brake). At first the brake (not ABS) light would come on/go off while driving (doing a right turn on a decline used to turn it off for a second) but now stays on constantly...I don't have a code reader but some of what I have read hints at a problem detected with the brake system. The brakes seem fine (slightly mushy/soft but still do the trick). There is no pulsating, squeaking/noises that come from the brakes when I use them and the fluid level is good.

The speakers in the car are messed up which makes me believe there is a wiring problem. The speakers are faded and only play treble but when it's rainy/humid the front right door speaker will come in and out sounding significantly louder with bass to it. Previous owner could have just blown them but the fact that it comes in goes with the rain makes me suspicious.

I just replaced the windshield wiper switch (part S3839 from O'Reilly) which the previous owner had broken and the washer fluid never worked (works fine now). This, combined with the fact that the triangle piece on the passenger door where the wires go down to the door (inside door, where side mirror is located) makes me think that there has been some tampering with the wiring. Another seemingly random issue is that the numbers on the odometer do not light up (Everything else on the dash works and illuminates)...not critical to fix, just figured I would mention it.

Can anyone tell me if the two issues might be related and how I might be able to go about testing? Advice on reliable/affordable code readers if necessary would also be greatly appreciated!

Your brake light sounds like a fluid level issue. Low fluid also indicates worn pads so please check those also. The speakers are probably just bad, these cars have separate tweeters and main speakers. The wrench light is often a transmission issue, when on the transmission shifts with high line pressure ( very firm shifts). The wrench light usually resets with a restart. The triangle piece on the door is probably off the fix the outside mirror, they break off the car if leaned on. The odometer is usually a failed resistor inside the speedometer, they are repairable. This is a common failure across all GM product lines.