This student guide is for Unit 4, Secondary Circuit, in the Engine Tune-Up Service portion of the Automotive Mechanics Curriculum. It deals with how to test and service the secondary ignition circuit. A companion review exercise book and posttests are available separately as CE 031 215-216. An introduction tells how this unit fits into the total tune-up service, defines new terms, and provides work activities on the introductory information. Seven performance objectives are covered: inspect and replace ignition wires, cap, and rotor; remove, clean, gap, and install spark plugs; analyze engine performance; perform a cylinder power balance test; perform a cylinder leakage test; perform a cylinder compression test; and test and repair transistor ignition system. Each objective is addressed in a separate section that includes these materials: introduction to the performance objective, performance checklist, list of tools and equipment needed to do the work activities for this performance objective, reading list, information sheets, and work activities that give hands-on practice in doing one part of the performance objective. (YLB)