Toyota Repair: 1998 Toyota Sienna Buzzing noise passenger side under dash

Question
Hi,

My 1998 Toyota Sienna XLE (automatic) 143,000 miles has been making an electronic buzzing noise under the passenger side of the dash.   It has had other electrical issues such as the D doesn't light up in the console panel when you put it into Drive.  The clock lights up but is very dim, and the driver's side window has an occasional issue, where it won't go up after being lowered.  

The indicator light for the tire pressure being off balance has been lit since the first time I replaced the tires - I was told this was an issue that can't be fixed.  

I've an issue with the air conditioner losing coldness and while it was getting warmer it seemed to make kind of a weird humming noise, but my mechanic recharged it, and added a leak fixative.  It seems to still be getting cold, but I mention it in case it could be related.  That was in the spring of 2013.

Apparently the check engine light has come on at least a couple times while my daughter has driven the car on the freeway.  I haven't noticed this but perhaps it is a new issue.

I've tried to do some research on the internet to troubleshoot this, but the only issue I found that was even close had advice indicating that the entire electrical system would need to be replaced.  

Do you know what I'm dealing with?

Thank you in advance for any light you can shed on this issue.

Answer
Hello, it seems there are a few problems that may or may not be related, has the van been in an accident? It may be a good idea to have the computer scanned for any diagnostic trouble codes due to the light coming on, most autoparts stores will do this for you at no charge, then let me know if there are any codes this will at least give me starting point.