Changing the battery should not set any codes. I don't think low oil pressure will set a code but could be wrong, I've got a 1050 which has a completely different engine management system. I would address the low oil pressure immediately as you could be doing serious damage if you run it with low pressure. You may just need to top the oil up. If that doesn't fix it I would change the filter and oil and take a close look at both for any metallic bits.