Could loose paper guides cause a P02 error on my Canon MP287?

Absolutely. Loose or misaligned paper guides are a common cause of paper feed errors, including P02. Ensure that the paper guides are properly adjusted to fit the width of the paper you are using. They should be snug but not too tight. If they are loose, tighten them carefully. Incorrect paper guide settings can prevent the printer from accurately sensing the paper's position.