Although math does not play a huge role in computer science, it's still somewhat important. The core courses that require math are in MATH1131 (as mentioned, with 3U assumed knowledge), MATH1231, MATH1081, and COMP3231.
In saying that, that's probably it.
But if you're treating computer science as just a backup, I would probably advise not rushing into it with MATH1131. Stick with the core business courses for now and try your luck for a bit longer. MATH1131/MATH1231 aren't actually prerequisites for any COMP courses, so you wouldn't be damaging anything by taking them only after you transfer into CS. You can study COMP on the side with MATH that way. So you don't have to put your WAM at risk if you're still determined to go into commerce.
(But if you'd rather make MATH work, I'd suggest at least learning the 3U course somehow. I know one of my mates could vouch for the bridging course for 3U, even if it cost him a few hundred. Alternatively taking MATH1011 before MATH1131 also works, but keep in mind that pathway is an extra $1K.
It's actually possible to do well in MATH1131 on only 2U. It's just known to not be an easy task.)