This book of pretests and review exercises is designed to accompany the Engine Tune-Up Service Student Guide for Unit 6, Emission Control Systems, available separately as CE 031 220. Focus of the exercises and pretests is inspecting, testing, and servicing emission control systems. Pretests and performance checklists are provided for each of the seven performance objectives contained in the unit. There are 23 review exercises that are short check-ups to let the student know how well she/he has learned the material for one or more work activities covered in the Student Guide. Answers to all of the exercises are found at the back of the book. (YLB)