These are most frequently under the dash and one side of the steering wheel. It may tell you where in your owner's manual. If not, I would find an Impala fan forum or subscribe to www.alldatadiy.com.
RepairPal Certified shops can diagnose and repair your 2007 Chevrolet Impala. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.