To change your security question, go to pge.com and sign in to Your Account using your current username and password. Select EDIT PROFILE & ALERTS (yellow button at the top of the page). This will bring you to the PG&E Preference Center. From there, scroll down to Profile and select Change Email, Password. Scroll down to Change Your Security Question. Use the pull-down menu to select your security question prompt, and then input the answer. Select SAVE CHANGES at the bottom of the page when you are finished.
If you are unable to sign in to change your security question, contact PG&E at 1-800-743-5000.