The "Very Low Quality" flag has a rather specific meaning, shown when you bring up the flags menu:
This question has severe formatting or content problems. This question is unlikely to be salvageable through editing, and might need to be removed.
The flag is intended for:
Severe formatting issues
Other severe content problems: This includes answers that don't attempt to answer the question.
Answers that are wrong, or vague, don't come into this category. Just vote the answer down, or make a comment explaining why you don't agree with the answer.
If the answer attempts to answer the question (even if the answer is wrong, or brief) that doesn't qualify it for VLQ flag.
For example, I would describe "read the datasheet" as not attempting to answer the question. However suggesting something that would not work, or would not help, is not very low quality. It's just wrong.