Since he wasn't a trained singer he probably had no clue what that is.
They could have had him listen to the song first and he could have imitated it. They did the same thing with Mel Gibson on Pocahontas. Mel Gibson had no musical background either he only did the singing because he wanted to and Disney couldn't say no to him.

Not really.. since you need to know the notes (ie high or low)

the reason that Scott Weinger didn't sing is because he couldn't read music.
Huh? He wasnt playing an instrument. You can still sing a song even if you cant read music.

the reason that Scott Weinger didn't sing is because he couldn't read music.

I'm not sure about Scott Weinger's case in why he didn't do his own singing. I'm having trouble locating an interview in which he was asked why he didn't his own singing.
I believe he couldnt sing as good as they wanted.
But really, it's actually kind of rare that the same actor does the voice and singing voice for characters in a Disney film. It's easier to count the examples who DID do both rather than the ones who didn't.
Snow White, Pinnochio, Cinderrella, Alice in Wonderland, Peter Pan, Sleeping Beauty, Sword in the stone, Jungle Book, Many Adventures of Winnie the Pooh, The Great Mouse Detective, Little Mermaid, Beauty and the Beast, Princess and the Frog, Tangled, Frozen, and Moana all had the same voice actors do the voice acting and singing.

Jonathan Taylor Thomas, Niketa Calame, Matthew Broderick and Moira Kelly didn't do their characters' singing in TLK either.
I think the OP's question could apply to any Disney film where that's the case.
But really, it's actually kind of rare that the same actor does the voice and singing voice for characters in a Disney film. It's easier to count the examples who DID do both rather than the ones who didn't.

Jonathan Taylor Thomas, Niketa Calame, Matthew Broderick and Moira Kelly didn't do their characters' singing in TLK either.

Linda Larkin, the speaking voice, was approached to sing, but she declined to sing as Jasmine because she claims she's not a singer as she stated in various interviews like these:
http://my.xfinity.com/blogs/movies/2015/10/21/“aladdin”-star-linda-larkin-praises-jasmines-spirit-of-activism/
and
http://www.mediamikes.com/2010/10/interview-with-linda-larkin/
So the casting director and Alan Menken had no choice but to find someone else to do the singing. And I'm sure by the time Lea Salonga was hired, Larkin had already recorded a fair amount of her dialogue and because the directors fought to keep Larkin in the role, they wouldn't replace her just because she couldn't sing.
I'm not sure about Scott Weinger's case in why he didn't do his own singing. I'm having trouble locating an interview in which he was asked why he didn't his own singing.
What we do in life, echoes in eternity.

Not sure that would have to go for the person that did the casting for this movie